We can boil the Plan Phase down into 3 main steps:

1. Calculate all forces acting on the vehicle (worst-case scenario)
2. Estimate Peak Power requirements
3. Estimate Energy requirements for range

1.   Calculate forces acting on a moving vehicle

Worst-case scenarios are those in which the resistance forces are the highest. Most of the time this means full power accelerations. We will estimate all forces acting on the vehicle using first principles and common sense.

In this particular case, I estimate that my worst case given how I plan to use this vehicle would be a 0-60 MPH acceleration in around 10 seconds on a 1% incline with 2 adults, a large dog, and some light cargo.

In order to do this calculation, we need to understand the basic principles of how a force is calculated:

$F = m \cdot a$

Or force is equal to mass times acceleration.

So how much mass are we talking about here? Vehicle + occupants + cargo.

So, let’s estimate:

The stock vehicle weighs around 3500 lbs, but we’re removing the ICE components and replacing them with EV components, so let’s call it a net-neutral swap when considering EV motor, inverters, OBCM, auxiliary components. Batteries are heavy, so let’s add 300lbs for this thought exercise.

Therefore:

Vehicle= 3800 lbs

2 adults = 350 lbs

1 large dog = 80 lbs

Light cargo = 50 lbs

Total mass to move = 4280 lbs (or 1941 kg)

We defined our expected acceleration in this case to be 0–60 MPH in 10 seconds, which would be 0 to 26.8 m/s in 10 seconds. Acceleration is change in velocity divided by change in time, so:

Going back to our Force equation we now know that

We will call this the Tractive Force $(F_{tr})$.

Cool, that’s the force we need to push the vehicle’s mass, but there’s more forms of resistance: rolling, aerodynamic and grade resistance forces also exist.

Rolling Resistance Force

Rolling resistance is a force that opposes motion of a tire. It comes from the internal friction of the rubber molecules when deformed under stress. At highway speeds, the majority of our EV conversion’s losses come from aerodynamic drag. At lower speeds, however, like stop and go traffic, rolling resistance is much more important.

Rolling resistance mainly depends on the vehicle’s weight, and the tire’s coefficient of rolling resistance, the latter we will be estimating based on standard values.

Where:

• $m$ is the mass of the vehicle in $kg$
• $g$ is the acceleration caused by gravity in $\frac{m}{s^2}$
• $C_{rr}$ is the coefficient of rolling resistance

Let’s assume a Coefficient of rolling resistance of 0.0115 on touring tires. (This coefficient comes from published SAE data mostly, but we will not get into specifics in this article.)

Aerodynamic Resistance Force

Aerodynamic Resistance force depends on more factors. Vehicle speed, frontal area, and overall drag coefficient affect it, as well as air density. We can summarize this force in the following equation:

Where:

• $\rho$ = air density in $\frac{kg}{m^3}$
• $C_d$= Coefficient of drag
• $A$= frontal area of vehicle in $m^2$
• $v$ = vehicle speed in $\frac{m}{s}$

In my worst-case scenario, Aerodynamic Resistance will be highest at 60 MPH.

NOTE: Coefficient of drag, frontal area and air density were estimated. Vehicle speed of 60mph was converted to meters per second.

Grade Resistance

When the vehicle is going up an incline, or grade, there is a component that is pulling it back. Think of a car rolling backwards when it’s parked on a hill: that’s the force that the motor has to overcome.

Where:

 $m$i s the mass of the vehicle in $kg$

$g$ is the acceleration caused by gravity in $\frac{m}{s^2}$

$\theta$ is the angle of road incline in radians or degrees

For small inclines we can assume $\sin(\theta) \approx 0.01$.

Therefore:

Total Force

Well, now we have all the forces at the defined worst-case scenario, so what now?

We know the forces that oppose motion: rolling resistance, aerodynamic resistance, grade resistance. We also know the mass of the vehicle and the acceleration we want it to achieve, so that gives us a tractive force.

This means that the motor needs to be able to make enough power to: 1) move the vehicle’s mass at a given acceleration and 2) overcome resistance forces.

This translates into the following summation:

2.   Estimate peak power requirements

Now that we’ve done the hard part and calculated all the forces acting on the vehicle in our worst‑case scenario, the next step is to translate those forces into power. This is where things usually start sounding intimidating, but the logic is actually very simple.

Power is just force applied at a certain speed. If we already know the total force the vehicle needs to overcome, all we need to do is look at how fast the car is moving when that force is highest.

In our case, the worst‑case scenario we defined was accelerating from 0 to 60 mph in 10 seconds on a 1% grade. At the end of that acceleration, the vehicle is traveling at 60 mph, which is 26.8 m/s. That’s the speed we care about for peak power, because aerodynamic drag is highest there and we’re still demanding acceleration.

We already calculated the total force required at that point:

So we can calculate the mechanical power required at the wheels using:

Where:

$P$ = Power in W

$F_{Total}$ = Total Force in N

$v$ = vehicle speed in $\frac{m}{s^2}$

Substituting our values:

That means we need roughly 158 kW of power at the wheels to meet our worst‑case performance target.

But that’s not the whole story. The motor doesn’t send power directly to the ground with zero losses. Between the battery and the wheels, we have losses in the inverter, the motor, the wiring, and whatever drivetrain components we’re using. A reasonable assumption for an EV conversion is around 85% overall efficiency.

When we account for those losses:

This tells us that, in our worst‑case scenario, the battery needs to be capable of delivering around 186 kW of peak power.

I like to add a bit of margin here — not because the math is wrong, but because reality always finds a way to be less clean than the spreadsheet. Temperature, component aging, voltage sag, and real‑world inefficiencies all stack up. Adding a 10% buffer is reasonable and keeps us out of trouble.

That puts our target peak power at roughly:

This number now becomes a key input for the rest of the build:

            •          The motor must be capable of delivering this peak power (even if only for short bursts)

            •          The inverter must be rated to handle it

            •          And the battery pack must be able to supply that power without exceeding current limits (Remember that Power = Voltage * Current)

3.   Estimate Energy requirements

In order for this conversion to be usable in my specific scenario, it has to be able to cover a certain range with a fully charged battery. The amount of energy available for propelling the vehicle is stored in the main high voltage battery, or the propulsion battery. How “big” should this battery be? And what does “big” mean?

Battery capacity is mostly measured in Watt-hours, or Wh. This unit is used because it tells us how much power (Watts) the battery can deliver over time (hour). So, then, how much power do I need this battery to deliver over time?

As you might recall from the original SPARK series, for our Energy Blueprint we can use an estimate of energy consumption per mile for different vehicle types.

Based on this table, I would say this is not quite a Small Convertible, and it might not be quite the Sports Car, but the latter is the category that I believe suits it best for a few reasons. First, it is a coupe, so not quite as light as a Small Convertible, nor quite as heavy as a Large Family Sedan. Due to its older, boxier design when compared to modern Sports Cars, I am going to estimate energy consumption at the higher end of this category around 350 Wh/mile.

But since this is a walkthrough, and I wouldn’t just blindly trust this number, let’s do a slightly more accurate calculation without needing to come up with OEM level simulations.

This vehicle will be used mostly in the highway at a steady state, with some city driving. I estimate longer highway stretches to be my conversion’s most vulnerable use-case since I wouldn’t want to drive 30 miles to run errands and finding out the hard way that I needed more highway range.

City driving with constant stop and start is not my main concern because regenerative braking will help us get some of the energy back into the battery and, in my particular use case, will not constitute the majority of my drive cycles.

How do I get to an energy consumption estimate per mile in highway driving? First, I need to understand the forces acting on the vehicle in this particular condition. For one, there’s no acceleration: highway driving is estimating constant speed, on flat ground. Constant speed means no acceleration. Flat ground means no grade. This means the only forces we need to overcome are resistance forces: Aerodynamic, and Rolling, both of which we calculated in the first section, but with one caveat: I want to cruise at 75 MPH, not 60 MPH. Using the same equations from section 1 we get the following forces:

Force times velocity is power. We know the force acting on the vehicle, and we know the speed:

This represents power at the wheels. What about power from the battery? Divide this by 0.85 to account for losses (efficiency).

Considering that Power is Energy over Time, and that at 75MPH we cover 75 miles in 1 hour, along with some other first principles magic that I won’t detail here, we get that:

I was close enough in estimating around 350 Wh per mile, but now we know with a bit more certainty.

In the Select walkthrough article I defined my range expectation to be 60 miles of combined driving. I will now estimate the energy required for 60 miles of constant highway driving, and will add a 20% buffer for city driving, passing, grades, extra electrical loads like lights, audio, cabin conditioning. I will also add 10% for lithium battery protection since these batteries shouldn’t be charged nor discharged fully.

Now the total 30% buffer:

Rounding, I would be happy with a 30 kWh battery pack for this application.

What now?

The energy estimation above is just the starting point for selecting a battery pack. We now know the energy we need to meet our goals with this conversion, but size may vary due to other factors. For example, we might find that the discharge rate of the available battery packs in the market (used or new) is not enough to meet our peak power requirement with the size we calculated. For example, a battery pack available in the market might not meet the peak current discharge to achieve our 204.6 kW power. In this hypothetical scenario, we have the option to look for another battery pack with a higher C rate, or we might add more modules to the readily available ones to increase the peak current capacity, even if the pack ends up being bigger than 30 kWh.

I will get into more details about motor and battery pack selection for this conversion in future articles of this walkthrough series.

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Sure, internet warriors and some corners of the media love to dunk on them. But here’s the truth: EV powertrains make a lot of sense in certain builds — especially in vehicles that were never that exciting to begin with. You know the ones. The cars that always felt like they were missing something.

That’s where the SPARK methodology comes in. This methodology was developed to help guide you step by step through the thinking and planning process of an EV conversion. We love wrenching, doing, and making, but I believe in sitting down and planning everything first to see if it makes sense.

Let’s walk through an example in which I will attempt to capture my train of thought in writing.

Select

The most important step in any automotive creation process is defining what we want the vehicle to do. The answer to this might be as simple as “I want it to look cool”, or it could be as complex as “I want it to reach a peak acceleration of 5.36m/s² while carrying a payload of 180 kg on a 1% grade AND look cool”. The more clearly we define our needs, the better the results will be, so the idea behind this phase is to come up with Engineering Decisions: a group of parameters that will translate into our basic requirements for this conversion.

High Level definition of what the vehicle should be

Let’s start simple and high level:

This EV conversion will be used for weekend cruising around town only, and maybe as a commuter every now and then. My commute is short and cruising around town is normally less than 20 miles total, but I’d love to have a significant buffer there, so having a real world combined total range of 60 miles would suffice. The vehicle should be able to drive in highways and city traffic, so top speed should slightly exceed the legal highway speed limit, let’s say around 85 mph. I don’t really need it to be quick, but the quickness of a small “hot hatch” or a sporty sedan would be great, so a 0-60 mph time that matches that of a stock FG2 Civic Si would be ideal. My wife, my dog and I would be the only passengers, and we don’t normally carry much cargo so no special request there. This would be a 3-season car: spring, summer and fall, it’d be stored during the winter since I live in Michigan and I don’t plan to use it on such cold and snowy weather. Since I have a level 2 charger at home, I would need the car to be able to take a J1772 connector and charge overnight.

Now let’s get more specific here and categorize the Engineering Decisions we need to make. The table below shows the Categories, Requirements and Engineering Decisions based on my text above.

These are objective parameters, though. Many types of vehicles could potentially meet these requirements and do just fine. We could achieve these goals with a Jeep Wrangler, a Toyota Matrix or a Ford Excursion conversion. So, this is where it gets personal, this is where we give it our touch.

In this particular example, I decided to use a 1990 Oldsmobile Toronado Trofeo as the donor car. I wrote a short article a while back, where I mentioned this car before, but here’s why it made the cut for this SPARK exercise:

It’s got that underrated ’90s futuristic styling, a front-wheel-drive layout that simplifies packaging, a surprisingly comfortable interior (this was peak Luxury Coupe Era, after all), and — most importantly — a forgettable 3.8L V6 that dragged the whole car down into the depths of mediocrity. That powertrain never lived up to the rest of the car’s ambitions, which makes it a perfect candidate for a second life as an EV.

Now that we’ve defined the purpose and design intent for this build, it’s time to turn those Engineering Decisions into real-world numbers. That’s what we’ll do in the next article – Plan – where we go from an idea, something that could even resemble a short conversation with a friend, to actual numbers so we can later select the components to power our EV conversion.

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But somewhere between the soulful and the soulless lies a third category—vehicles that almost had something to say. Cars that were close. And often, what held them back was the powertrain. In these cases, an EV conversion isn’t just a performance upgrade—it’s a second chance at identity.

In this article, I want to share five vehicles that I believe would benefit immensely from going electric—not because of speed, torque, or efficiency, but because an EV swap would finally bring their original design ethos to life. We’ve talked before about how EV conversions can be emotional, not just logical. This is that idea, taken to the next level. NOTE: this list is not in any particular order, so this is not a “top 5” list. Just a list.

1. Geo Tracker

The Geo Tracker was, in my opinion, one of those vehicles that just looks cool. Its cartoon-y looks, relatively decent (for the price) off-road capability, and its low price point made for a very interesting value proposition back in the 80s and 90s. However, its powertrain was just there, existing. Serving a purpose, sure, and getting the job done, but it was just not something that takes your breath away, nor something you wake up thinking about. With a modest EV powertrain, and a combined range of around 80 miles this would be a very interesting thing to drive around town, or maybe take to trails nearby. Immediate pedal response, loads of torque and a quiet ride with the top down would make this a very interesting weekend cruiser.

2. Chrysler 300

Many iterations of this vehicle have won the hearts and minds of a lot of people. Since its reintroduction in the 2000s, we’ve seen this affordable luxury sedan boast a decent V6, a brawny 5.7L V8 and even a delightful 6.4L V8. Though the V6 was a decent powerplant, with its latest iteration producing close to 300 hp, I personally believe an EV powertrain would complement this vehicle’s luxurious aura perfectly. Smooth suspension, comfortable interior and an exterior design that sets it apart from the “lesser” sedans of its class, an EV powertrain would give a base model Chrysler 300 what it lacked from the factory: torque, unparalleled smoothness and a technological touch that the V6 just couldn’t provide.

3. Ford Escort ZX2

This, to me, was a very interesting product proposition in the 90s and 2000s. The reason is simple: a compact, 2 door coupe, that was not trying too hard to be sporty, luxurious nor aggressive, that delivered decent fuel economy, interior space, and features for every day commuting. I just love cars like this because of their uninteresting nature, yet quirky design, that delivered nothing more than what they promised, but seemed to have something more. Though very far from a sportscar, I believe the torquey nature of an EV powertrain would elevate the experience of this “sporty economy coupe” to a very decent autocross platform. Make no mistake, though: a ton of power on this platform would, in my humble opinion, ruin the experience. But with a decent amount of power, immediate and smooth torque delivery, and probably a realistic range of 20 to 30 miles to keep battery mass on the lower side, this would become a VERY interesting autocross rig. You would definitely have to tow it to the event and back, and maybe keep a generator handy for charging it between sessions, but fun isn’t always simple!

4. Oldsmobile Toronado Trofeo

I think this is my favorite proposition of this list because of a very simple reason: its futuristic design. Now, think of this vehicle in terms of the design ethos of the era, and what the vehicle was supposed to represent to General Motors in their product portfolio at the time: the luxury coupe class was booming, and luxury has many different meanings. For some brands it was chrome and leather, for others it was size, presence and power, but Oldsmobile chose a different route: technology. With its CRT Graphic Control Center to control everything from audio, HVAC and trip computer, its plush interior, and its aerodynamic design with American presence, the Toronado Trofeo was appealing to people interested in “the future”. I love this idea, but I do not love its 3.8L V6. Not from its specs on paper, not from how it drives, and not from how it fits into this idea of “the future”. Plus, its Front Wheel Drive configuration was definitely not adding to the experience of a driver’s car. So what about this beautiful futuristic car, reimagined with a decent amount of power (not too much since it’s FWD… we can talk about why in a different article), a range of about 100 miles, and the smooth pedal experience only an electric machine can provide?

5. Chevrolet Astro Van

The utilitarian addition to give this list a solid foundation. “Why would you want an electric Astro Van?” you ask. Because why the fuck not. Tons of space for batteries and cargo, enough space for a powerful DC motor, and a platform that can take a beating, this would be a great EV conversion to either haul things around town, or do crazy burnouts, or maybe take to the drag strip, or maybe even off-road. I think this conversion can do it all, other than a road course or autocross… unless…?

Look, after all, EV conversions don’t make a lot of sense for the everyday enthusiast, nor should they. Human beings have something driving us to create. We create life, we create poetry, we create visual and auditive art that fills our hearts. This right here is creating. Using our hands and brains to meditatively put things together to create something. It can be abstract art, it can be building a table no one needed, crafting the most useless coffee mug from mud… or slapping a Tesla rear drive unit onto a 90s Astro Van, but creating something is part of our nature. Try creating something every time you can!

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What makes a car engaging, then? I think the industry has figured it out, as I’ll try to convey in this article, but making a modern enthusiast car isn’t as simple as it might seem to some people. Regulations, overall market behavior and safety standards have become priority, and rightfully so, in order to protect consumers, provide them with the most value, and, yes, create shareholder value. As ironic as that last statement might seem, it’s true: a corporation that sells vehicles at a mass scale cannot survive if investors don’t put their money into it, and they won’t unless they get more money back than what they originally put in, right? That’s shareholder value!

So, what should an enthusiast do? Well, I think some OEMs are doing the best they can to provide enthusiasts with great products even under today’s market and regulatory constraints (there are many examples of this, thankfully), and some other OEMs even exist only to provide these types of experiences (Ferrari?), but I think us DIY enthusiasts can and should take control of some of our desire for engagement.

What makes a car engaging?

Mechanical Feedback

One of the most engaging aspects of driving a car is the feedback you get from the machine. From the accelerator pedal response, to the mechanical sound and feel of shifting gears on a manual transmission, to the weight of the steering wheel on different surfaces and driving conditions, these characteristics make the vehicle feel special. If you’ve ever heard that BMWs have a very numb steering feel, then you understand what we’re talking about here.

Sound

The most important aspect of an engaging car is, hands down, the sound it makes. Or sounds. Exhaust note is one of the most important aspects in an ICE-powered car, but it isn’t the only thing. Tire noise, suspension sounds and even certain cabin rattles make the experience more or less enjoyable. Engine sound, apart from exhaust note, is also critical. I make the distinction between engine sound and exhaust because it’s not always about a loud exhaust, or a particular exhaust note, it’s also the rotating components, firing order, and intake sound. My Civic Si had a horrible exhaust note, but the engine’s sound was very enjoyable, particularly when that VTEC kicked in.  

Vehicle Dynamics

The notion of old, long vehicles driving like boats is not that far-fetched. They do drive as though floating on water. Body roll was crazy, squatting and diving under acceleration seemed excessive, but comfort was unmatched. On the other hand, a modern Mini Cooper is like driving an oversized go kart: nimble, quick to turn, and planted under most driving conditions. The characteristics that make up what we call ‘Vehicle Dynamics’ help define the vehicle’s mission, and with it, its character. You wouldn’t want a high-powered car that drives like a boat, unless you’re into Hellcats.  

Emotional Connection

This is what it all boils down to for me: emotional connection. I’ve had the privilege of owning different cars throughout my lifetime, from cheap shit boxes to decent “luxury sedans”, but the ones I have enjoyed the most possess certain characteristics that make them very special to me. For one, the vehicle has to be part of my life: road trips, adventures and friendships are made, shared or experienced aplenty with or around this machine. The second most important is working on it myself. Whether maintenance or repairs, the effort, care and frustration involved in keeping the car in mint condition helps me bond with it. I don’t develop this emotional attachment to a car whenever it only serves as A to B transportation, has a warranty, and needs nothing from me.

An engaging EV conversion

Making an EV conversion engaging requires manipulating the things we talked about above in such a way that it becomes an activity to drive it, not an afterthought. We want to make it more like riding a horse: it requires skill to read into the horse’s behavior, to know what it might do next, to know how to act such that it in turn reacts in an expected manner. EVs are so advanced and so toned down in this regard that we know we can step on the accelerator pedal and it goes, step on the brakes and it stops, engage some level of autonomous driving and it will basically take us where we’re going. That is not the case with true engaging vehicles.

We want to hear the motor spinning, we want to hear some tire noise, to feel some steering feedback. The accelerator pedal is not only a control surface for altering vehicle speed, it’s also a portal into weight distribution, traction feel, and sometimes unexpected behaviors that require your full attention. Shifting gears is optional, but highly rewarding in many cases. Even quick shifting automatic transmissions have a high level of engagement under the right circumstances. A car might need to be uncomfortable in order to feel engaging. Maybe Recaro bucket seats are not ideal for long road trips, but they do a hell of a job for late night city cruising with the boys. Engagement comes from NOT being able to drive a car if you’re texting or looking for the right song on your Apple CarPlay deck; the car should demand your full attention.

So, with these thoughts I would encourage you to think deep about this question: how do we make an EV conversion that’s engaging? Converting a car is one thing and that is the most engaging part of this whole community, but once it’s converted, how do we make it remarkably fun?

NOTE: There’s also a fine line between engaging, DIY and unsafe. We do NOT want to surf that line. We do not want engagement to come from the adrenaline of not knowing if the car will stop, or if the car might catch on fire. This isn’t a rally race in the 70s. We’re talking about a vehicle that might be driven on public roads, with innocent bystanders that do not care about your enthusiasm but about making it home to their families. So please do not come here with those “adrenaline makes it fun” or “unreliable is engaging” bullshit stories. That’s the equivalent of “street takeovers are car culture”. They are not. Be a responsible DIYer, please.

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I know that the previous paragraph sounds like a mouthful, so if you’re still reading, here’s my point: innovation is not owned by corporations. Corporations CAN and DO innovate, but nothing stops you from trying it yourself, not even in the EV world, where technology seems so complex and overwhelming.

What does innovation have to do with EV conversions? EV conversions are nothing new, the technology has existed for longer than we think. But innovation is triggered by exploring, playing and trying new things. Tinkering.

Build a life of fulfilment

Kids play, animals play, and adults should try it to. Playing is the act of exploring our environments, and it’s a powerful tool to learn new things. In adulthood, it could even be a way of leading a happier life.

Fulfilment is something we all strive for, but not everyone understands what it might mean for themselves, so here’s a quick tip: if you’re reading this blog, most likely you like to build things, and maybe that is part of your life’s fulfilment.

Going back to the first article of our SPARK methodology series, you might recall that I suggested EV conversions are a form of expression, more so than a strictly useful, purpose-driven activity. In most industrialized nations today, an electric vehicle can be bought from the used market at a relatively affordable price in comparison with some of their ICE counterparts. So building an EV conversion for the sole purpose of transportation does not make the most sense (in most cases!).

So why would anyone build an EV conversion?

Building things makes us feel joy. It makes us feel capable, useful, and fulfilled.

When someone builds new things and uses them, there’s this feeling of “hey look what I did!”. I think it’s an instinct, possibly an evolutionary trait that causes amusement, joy, hope, which we want to share with the world. How many times have we fixed something seemingly insignificant and wanted to share it with our significant other, friends, or family? Or even social media!

Have you ever searched YouTube for tutorials on how to fix things? (Rhetorical question, I doubt anyone still reading this blog would answer ‘no’) These tutorials are very easy to find for most things; there’s always a person very proud of what they did trying to share it with others. This is no coincidence; I strongly believe it is evolution unfolding right in front of our eyes. Maybe it’s a tool to spread knowledge, generate a sense of community, or create hope in others that things can be better if we put the effort.

Imperfection as a tool

Building things = fulfilment. But what should we aim to build? Honestly, whatever you feel like. But keep it imperfect.

OEM’s need to keep things very efficient, precise and controlled in order to replicate the product at a mass scale. Corporations have mastered the art of producing seemingly identical products at a scale our ancestors would have never imagined, and that has changed the world. The USA won World War II mainly thanks to the military industrial complex. Many people have access to food, shelter, clothing, and medicine thanks to mass scale production. We have cars to love thanks to it too.

But we tinkerers don’t have to do that. We don’t need to be super precise with every little measurement, material or calculation. Imperfection is part of what makes things interesting to build: how many trips to the hardware store does it take to install a supercharger? Or replace a clutch? Things sometimes won’t go well, and for certain projects, it’s for the better.

I advocate for imperfect projects even though I make a living trying to achieve the ever-elusive idea of ‘perfection’ at an OEM. The reason why I do this is simple: I see projects, such as EV conversions, as a form of fulfilment; something that helps me translate my knowledge, skills and passion for learning into a tangible (and hopefully drivable) object. It makes me feel like playing with Legos or building cities out of carboard boxes for my Hot Wheels cars. It causes frustration that can be overcome by learning.

That’s why I think imperfection is a tool. Use it.

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“Energy efficiency”, “lower emissions”, “greenhouse gases”, these are some of the terms that have been mainstream in the automotive world for decades now. Since the Arab oil embargo of the 70s, the importance of lower fuel consumption, and lower tailpipe emissions has been at the forefront of powertrain design. However, I feel that things drastically changed in the mid-2010s when the industry and the consumer base started noticing the advantages of electrification: lower fuel consumption, lower tailpipe emissions, and in some cases, even better drivability.

Hybrids stopped being “cars for hippies” (Toyota Prius?) and became interesting value propositions. They also became part of the enthusiast community in some cases, like the affordable and efficient, manual transmission hybrid Honda CRZ, or the beautiful and impressive Acura NSX (ahead of its time, IMO).

But while this was happening, we (the automotive industry) were programming our consumer base to expect more, and we did that by making things more complex. Plug-in Hybrid Electric Vehicles (PHEVs) are an engineering marvel, for example. A vehicle that can be driven in all-electric mode, hybrid, or ICE only? You have 2 powertrains in one car! Sounds amazing, and it is in many particular use cases. But the majority of our efforts were put into making complex systems reliable, affordable, and efficient. We gave people what they wanted, which is very important, but some of the essence went away.

I’m not saying it’s only because of OEMs that the essence of automotive brilliance was affected, it’s a mixture of market behavior, government policies and corporate dynamics. But the fact is that emotional products are not as common as they were. People were more in touch with their cars in the past, owner’s manuals taught you how to test a spark plug, adjust your valves or replace certain components for servicing. Today owner’s manuals give you the bare minimum information about servicing your car since OEMs prefer consumers take them in to the dealership for service. And more so for hybrids and EVs; the technology relies so much on controls systems and software that servicing at home becomes more of a problem to both consumer and OEM.

I personally love hybrids. I also love EVs. I also love ICE. I’m not saying what the industry is doing is wrong: I am passionate about the industry and I believe the complexity is needed and justified.

What I’m trying to say here is: think of EVs beyond their efficiencies. Think of them as a new form of transportation that could be as emotion-driven as the automotive creations of the past. They will not replace ICE in that regard. No EV could possibly elicit the emotion of hearing a V12 scream, or a cammed-V8 cold start.

But they don’t have to! EVs can cause their own emotions. Speed, acceleration, quietness: maybe these are not the characteristics that will inspire a generation, but there might be some others. Range and instant torque are great, but that’s not what motivates me to drive one.

The smoothness of torque, the feel I get from regen, the ability of stopping overnight during a long road trip, connecting it to a charger and waking up with “a full tank”. That’s what I love about my own EV. But that’s just me. And that doesn’t replace the rumble of my V8, or the mechanical feel of a manual transmission, or the pride I get from maintaining my old carbureted sport bike. I don’t want it to.

I encourage you to pay attention to EVs from a different light: look at what they give you beyond efficiencies. Make a list, maybe even share it here. It might be hard for the enthusiast community to think of new forms in which EVs can connect to our emotional selves since we grew up wrenching, changing oil and listening to different exhaust notes and vibrations. But let’s give it a try. EVs are here to stay, anyway.  

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This topic is a very interesting one to me, personally, and I want to share my thoughts about doing a first EV conversion from the standpoint of a “student”, so to speak, since I have never done one myself.

What would MY first EV conversion look like?

 I’m going to freestyle this section since I think “flowing” through it will make it much more enjoyable to me, than would following a strict process like we do at the OEM level. This is very important for me to emphasize: enjoy the process. It feels slightly contradictory since we spent months writing a whole series on how to design an EV conversion and prepare for the project using our SPARK method, which seems a bit square, orderly and at times “boring”.  The idea behind SPARK, though, is to introduce you to many concepts, systems, and ideas about EVs in a systematic way. You can follow that system blindly, or you can grab bits and pieces at your own pace.

Now, have you ever thought about Harley-Davidson and the ethos behind their motorcycles? I’m not a Harley fanboy, I don’t own one, and I didn’t grow up dreaming of owning one, but I recently learned more about what most people love about them: simplicity. Nowadays the automotive industry has been plagued with all sorts of vehicles that seem bland: white SUVs with huge screens, blind spot monitoring and an engine so boring it hurts. These things are engineering marvels, but we have grown so accustomed to great engineering, powerful engines and comfortable rides that some of us have become bored with the offerings. The motorcycle industry, though slightly different in this regard, seems to be heading this way. Fuel injection, catalytic converters and even electrification have been taking over showrooms for years now, and though more capable, clean and reliable than ever before, some people want something else.

Enter simplicity. Harley-Davidson motorcycles, as described by purists, have always been “easy to work on, simple and dead-reliable”. What do these people mean? Well, you just have to look at what they were: a carbureted, air cooled, V-Twin engine that had tolerances so wide it could withstand abuse and neglect. Yeah, these motorcycles have a reputation of leaking oil and making more noise than power, vibrating themselves into a pile of chrome pieces in your garage, but we have to look at the idea behind their design.

You see, these machines had almost no fluff: engine, lights, starter, drivetrain. That’s it. Yeah, they weren’t the most efficient, quiet, refined or powerful machines, but they got the job done and they could be serviced anywhere. You never had to worry about an old school Harley “tripping a check engine light”, it ran or it didn’t. If it didn’t you serviced it, plain and simple. No dealer appointment, just a few beers and a wrench.

Why am I rambling about Harleys, the modern automotive industry, and boring engineering? Because I believe my first EV conversion, and maybe even yours, should aim to be the Harley of EV conversions: dead simple.

It’s easier to complete

I’m an automotive engineer, and I am a certified gasoline engine technician. This does not make me a SKILLED technician. I sometimes know what I’m doing, but most of the time I’m searching YouTube for video tutorials, googling shop manuals, and double checking the right-hand rule (righty tighty, lefty loosey?). This, combined with my overall knowledge and experience gives me the confidence to tackle SOME projects. But practice makes perfect, and I have 0 practice converting an ICE powered vehicle to EV.

Some of you will have much more experience, balls and knowledge than I do, and by all means, if you want your first EV conversion to be a dual Tesla swapped Corvette, go for it. And share it in the comments. But I assume most of you will want to attempt something easier.

Going all Harley on my first EV conversion allows me to focus on a few systems to get them right, and gives me the ability to finish a project in a shorter period, which I appreciate for my first attempt. I can upgrade later.

Simplicity

Cool, simplicity. What does that mean for an EV conversion? This section will try to convey what I’d look for in terms of components for my first conversion.

Worth noting is that I would focus on kits and/or brand-new components: I want to have the technical support I might need from the supplier, and I want to have as much technical documentation or previous experience from other builders that I can access online. I want to make this process as simple as possible so I can get the first one done the best way I can.  Remember: my focus here is on the conversion process itself, not on the selection process, nor the process of adapting recycled components, or building my own battery packs. Just the conversion.

Motor

The simplest motor one can choose is a DC brushed motor. Sturdy and battle tested; this type of electric motor can do it all. All, but regenerative braking, that is. Harleys aren’t efficient either, so that’s a hit I’m willing to take.

These days, however, DC motors are not the cheapest systems, especially when dealing with brand-new components, or full conversion kits. AC motors have come a long way in the EV conversion market, and their controllers are very advanced, offering extensive customization and very useful features like regenerative braking.

Having said all of this, my first choice in today’s market would be a simple 3 phase AC motor. I won’t get into specific details about which particular product I’d choose since I haven’t done the full calculation, that might come at a later time. Just think of this: I want something that works right out of the box, has enough power, is air cooled, and doesn’t require a lot of maintenance.

Battery

I’d go for a small capacity battery pack, something that gives me a few miles of range, maybe 50 (I’ll define this in future articles). I would go for something coming from a kit too, that way I can guarantee the BMS included has been tested with the pack I choose, and I have some support from the supplier. I don’t have a preference for chemistry at this point; I’d even go NiMH if the price is right.

Charger

My OBCM would be something small, probably something around 3kW since my small battery pack and low range expectations don’t really require fast charging or multiple charges a day. This is a project for cruising around town every now and then, not my daily driver.

DC/DC Converter

My first conversion wouldn’t have AC nor cabin heat since I don’t want to deal with liquids or gases (coolant and/or refrigerant gas), so I wouldn’t need more than 1000W.

Auxiliary Systems

Brake vacuum pump and an electro-hydraulic steering pump would be the only auxiliary systems I’d consider. The electro-hydraulic steering pump would be optional, honestly, since I’m not aiming for comfort and that component adds complexity. If my donor vehicle has a hydraulic power steering system, and my budget allows for it, I’ll do it, otherwise I won’t sweat too much (pun intended, I’d definitely sweat without AC and power steering).

Stating the obvious

Honestly, I don’t think I added much to the discussion in terms of technical expertise, creativity or ground breaking advice in the previous paragraphs, but that wasn’t the intention. Today, my intention was to state the obvious: simplicity is king.

We live in a world where, for many people, technology seems more advanced the more complex it is. The harder it is to understand, the more some people value its impact to our society, environment, etcetera. Now, I don’t want to paint myself here as the #1 fan of simple technology; I make a living developing complex hybrid vehicles with many failure points and the simplicity of a space ship, and I love them. But truth be told: I think our society would benefit from admiring simplicity, more than screens, apps and overwhelming networks.

Many car enthusiasts today complain about manufacturers not selling fun, simple, lightweight vehicles with manual transmissions and an analog tachometer. But the overwhelming majority of people prefers a machine that thinks for them, a dealership that cares for it, and a driving experience that doesn’t feel like an activity to engage in. We are absorbed by our phones, our computers and our tasks so much that driving from work back home seems like an interruption to the never-ending flow of information from our devices to our conscious minds.

Driving should be an activity that requires attention, skill, and time. There was a time when moving from one place to another was done by walking through dangerous terrain, more like a survival skill than a pleasurable activity.

Have you ever heard of the saying about a dog slowing you down if you take them on a hike with you? “Maybe that’s the point” is what they say. So, here’s my thought: driving a machine that requires thought, skill, care and understanding might slow your day down.

Maybe that’s the point.

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So what are we “kicking off”, exactly? The project has already started from the moment you went through the Select phase making your Engineering Decisions and selecting a donor vehicle, Plan phase defining your Energy Blueprint, Architect phase outlining your Component Strategy, Route phase drawing your Integration Map, and now it’s time to define your Operational Readiness Profile in this Kickoff phase.

Your EV conversion is closer to reality, from definition to assembly, and now that it’s all put together, we have to make sure that it is WELL put together. No one wants to go through a complicated design and build process just to find out that the conversion will break down a few miles into your maiden voyage. But, how do we make sure the build was successful? What does successful even mean in this context? We are about to find out.

Validation – confirming your EV conversion build

Validation is a common term in the OEM world – it means conducting testing to confirm that the vehicle, system or component meets the objective it was designed to fulfil. In other words, they make sure it works the way it should before selling it. You will be conducting validation to make sure your EV conversion does what you designed it to do.

We have to categorize your validation efforts into two main activities: Basic Checkouts and Engineering Checkouts. The former is a safety checkout where you will make sure that your vehicle is safe to drive and that you have full control of it. The latter is a process to validate that your EV conversion meets the requirements outlined in your Engineering Decisions.

Basic Checkouts

Before we talk about the specific checkouts, a note of caution. Bolded and underlined to highlight its importance:
All Basic Checkouts MUST be performed with at least another person helping (this is called  the Buddy System) and with wheels off the ground to avoid the vehicle potentially jolting forwards or backwards.

Please stay alive, safe and healthy when doing all of these checks. It is imperative to follow safety protocols and common sense. Never work alone when dealing with High Voltage systems. Never. Even if you are experienced.  

HV wiring checkout

The High Voltage system is, obviously, critical for your EV conversion, both in terms of it’s performance (wouldn’t work without one, eh?) and safety.

According to the SAE (Society of Automotive Engineering), anything above 60V DC or 30V AC in an automotive application is considered High Voltage. This triggers a lot of different requirements in the industry, for example: any system above 60V DC needs special High Voltage connectors, special safety interlocks, PPE (Personal Protective Equipment) and specific training for technicians, color coding on cables and connectors, among other things.

Even though some EV conversions are not considered High Voltage according to this specification, for example 48V or even 24V conversions, in the context of our Basic Checkouts, the higher voltage system will be considered HV (in this example, our 48V system will be HV, our common 12V system will be Low Voltage).

All HV wiring needs to be visually checked to confirm there are no worn out cables, broken or uncovered connectors, or flat-out missing cables. Wiring also needs to be verified to have been connected correctly according to your Integration Map, and a multimeter needs to be used to confirm continuity and voltage in the proper places.

Isolation is yet another important aspect of an EV, particularly a DIY conversion, so special multimeters must be used to guarantee proper isolation between the HV circuitry and the chassis, cabin, and even other LV systems.

LV wiring checkout

Most automotive electrical systems run on 12V: engine starter, radio, blower fan, power windows, heated seats, you name it, it most likely runs on 12V.

Some systems in your EV conversion will be kept in place from the donor vehicle, things like lights, powered windows/locks, radios, cluster gauges, among other things. But some others will have to be added or modified.

Make sure all your Auxiliary Systems, discussed in the Architect Phase, are checked out. Things like brake vacuum pumps, DC-DC converters, steering assist systems, cooling systems. These all have to be checked to have power and appropriate functionality. Do the pumps run when commanded? Will they stop when expected? Does the DC-DC converter charge the 12V battery at the proper voltage? Fans operate properly?

The specific checks your conversion requires will depend on the components you have selected (Component Strategy) and how they are connected (Integration Map).

Contactor Control

This is super important to verify with at least another person in the garage, and with wheels off the ground.

Contactors are the main switch that connects the battery to the rest of the HV bus. Their operation is critical to the safety and proper functionality of the electric powertrain, so validating their operation before attempting to put wheels on the ground is necessary.

The first thing you need to confirm is that the contactors follow commands: do they close when commanded to? Do they open when commanded to?

The next thing to verify is that they properly isolate the battery from the rest of the HV bus. This can be done in many ways, for example, voltage can be checked at the input terminals of the motor controller with contactors open. No voltage should be expected when they are open, and battery voltage should be expected when closed.

Another thing to verify is that the Emergency Stop switch (which should be installed in every DIY EV conversion) properly opens the contactors, even under load. A quick test is to close contactors, and while making the electric motor spin via the accelerator pedal, actuating the Emergency Stop, or E-stop, expecting contactors to open and torque to the wheels to stop.

Torque Control

Simple enough, the idea of a Torque Control check is to verify that the motor follows the accelerator pedal commands: pedal is actuated – torque at the wheels. Pedal is released – no torque at the wheels.

Do not put wheels to the ground until all checks are passed safely. Modify or fix whatever needs fixing until everything passes and you are 100% certain that your build is safe to lower on to the ground. Once wheels are grounded, the fun starts: your first drive.

Engineering Checkouts

The first drive of any build is an interesting feeling: pride, fear, anticipation. Enjoy those feelings; even though these validation efforts are necessary, the main objective is to enjoy the build!

Now that your conversion passed the Basic Checkouts, it’s time to make sure that your EV conversion will perform as expected. Remember your Engineering Decisions? You will need to.

Total vehicle weight

One of the most critical decisions you made in the Select phase was payload. This means how many passengers, how much luggage, towing, or anything that affects how much the vehicle weighs. Back then it was an estimation: you wouldn’t be able to predict the weight of the batteries, motor, controller, etcetera. Now it’s time to weigh the vehicle.

It’s time to weigh your conversion! There are specialized shops, mainly for racing, that have 4-corner weight scales, which would be ideal to determine weight balance. How far off from your estimates is the conversion? This can help you get an idea of how much the performance of the build will differ from expectations: if the vehicle weighs more, acceleration, grade and speed might suffer. If it weighs less, then it’s the other way around.

Maximum grade

Time to take it for a spin! Go to the steepest hill you have nearby and see if the acceleration and speed performance going up the grade is acceptable to you. Make sure the hill is within range!

Maximum speed

This is a tricky one. If our designed maximum speed exceeds legal limits, DO NOT TEST ON PUBLIC ROADS. If it is within the limits, then by all means, do it safely.

Maximum acceleration

Make sure you are doing this test on a safe space. Never do it in crowded areas or high traffic roads. Always follow law and regulations.

Grab a chronometer or some sort of tool to measure 0 to 60 time. Does it match your expecations?

Desired range

Plan a short city drive and a short highway drive. See how much battery SoC (State of Charge) you use and the number of miles you cover. Even though SoC is not linear in most cases, you can extrapolate a bit to get an idea. If driving 50 highway miles used 50% of the battery, then an estimated 80 to 100 miles is your range. City driving will be a little less, so if 30 miles of city driving use 50% of the battery, then an estimated 50 to 60 miles of range is what you get.

Thermal stability

Plan 2 different drives: one short and aggressive one where there’s a lot of acceleration, braking, steep hills and the like. The other one will be a steady highway drive, preferably up a slight incline.

The idea here is to monitor temperatures of your main components: battery, motor, controller, DC/DC converter. Some components report this temperatures through software or a scan tool, some others will require thermostats that can be bought from a hardware store. Make sure your components never exceed their manufacturer-recommended temperatures under normal driving conditions. Normal driving conditions = what your Engineering Decisions call for.

Charging time and thermal stability

Charge your HV battery with the charger you selected and make sure your charging time matches what you estimated, and that the thermal stability of your OBCM, Charging Station and HV battery is achieved.

Calibration – fine-tuning your conversion’s behavior

Calibration is the process of adjusting parameters on your controller, DC/DC converter, BMS, and any other important system, in order to obtain the behavior you expect from your vehicle. Just like a “tuner” (or calibration engineer, in OEM jargon) modifies fueling, spark, and other parameters on a fuel injection system for an ICE, you will have to modify some parameters in your EV conversion to achieve your desired outcomes.

Throttle Mapping

Throttle is a word commonly used to refer to the accelerator pedal. However, a throttle is a throat, or a gullet, and it applies only to Internal Combustion Engines (ICE), since the accelerator pedal actuates a valve that allows more or less air into the combustion chamber, and with it, fuel.

An EV does not have a throttle, per se, but it’s a common term to use, so we’ll give it a partial pass. Mapping the accelerator pedal, or Throttle Mapping, is something that can be adjusted on some EV controllers, and it is basically how much torque the motor needs to generate according to the pedal position. Mapping these parameters allows for greater flexibility in terms of vehicle behavior: you can make the vehicle respond very aggressively at the slightest accelerator pedal movement, or you can make it respond slower, providing a lot more “definition” in pedal control for slow maneuvering.

Maximum/Minimum Torque Limits

The motor has a maximum and a minimum torque: it can’t make more than the maximum, or less than the minimum. But these parameters can also be “artificially” modified. For example, if the motor can have a maximum torque of 100Nm by design, but you find that so much torque is problematic, maybe breaking axles, or causing too much wheel slip, some controllers allow you to modify this limit. Say you modify it to 80Nm maximum, so when you fully depress the accelerator pedal, the motor will only give you 80Nm, not 100Nm.

Regenerative Braking Levels

Some controllers allow for regenerative braking (as discussed in the EV motor selection article of the Architect phase of SPARK) and some others even allow for various levels of ‘regen’. The idea behind varying the amount of regen is to modulate the driving experience. If there is too much regen, when you want to release the accelerator pedal (tip-outs, in OEM jargon), the vehicle will decelerate very quickly, which might be uncomfortable. Varying these levels to your liking will enhance your experience with the vehicle, hopefully making it more enjoyable.

Component Temperature Limits (motor, controller, battery)

Some components are designed to work together with their controllers, and some are not. Those that are designed as plug and play might have their controllers programmed for their temperature limits, allowing for better control, more longevity, and safer operation. However, if the controller used does not have temperature limits programmed, it is paramount to get these values from the manufacturer and program them in. This allows the controller to react to increases in temperature, lowering their power output to preserve them, or sending a signal to you, the driver, so you can take action as needed. Always monitor temperatures and get used to their normal values in your specific drive cycles and modes of operation!

State of Charge (SoC) limits

These limits can be set by the manufacturer of the battery cells, modules, or pack, and are mainly used for cell longevity. Both the BMS and the motor controller can use this information to lower, or completely cut, power from the battery pack to the HV systems in order to avoid over-discharge of the cells. It can also be “artificially” modified, for example, to stop charging once the overall SoC hits 80%. This can be overridden when your intention is to go on longer trips, so the system would then allow charging up to 100% SoC.

Voltage thresholds (cell, pack, controller)

Critical information for the system, voltage thresholds allow the controllers to cut operation of certain systems if under or over voltage events are detected in order to protect the occupants, and systems.

Battery Cell Balancing parameters

Some cell balancing can be fine-tuned in the BMS. The idea of cell balancing is to keep the cells safe and efficient, as internal cell resistance varies with varying SoC. You don’t want one cell at 20% SoC while the rest are at 65% SoC, this might cause over discharging of one cell, which could damage it.

Current Limits

These limits come from supplier specifications of the motor, inverter and battery pack, and must be programmed into the controllers to avoid damage.

Cooling system activation thresholds

If a cooling system is equipped, you have to decide when to actuates fans and pumps. Keep in mind that over-actuation is a thing, and it is possible that you are wasting energy by enabling these systems when they are not needed. On the other hand, if your thresholds are too high you risk damaging your components due to overheating, either immediately or on the long run. Calibration is an art!

Charging parameters

Charging curves are important to optimize energy storage and temperature stabilization of battery cells. At different SoCs, cells are more or less efficient at storing energy. Less efficiency = more heat. The more current you put through them at their most inefficient point of operation, the more heat they dissipate. You have to decide whether you can handle the heat dissipation and take the efficiency hit for the sake of charging speed, or if you want to lower current until the cells reach a more efficient point of operation. Always refer to manufacturer specifications and data for making these decisions.

Your Operational Readiness Profile (ORP)

So you’ve validated and calibrated your conversion. It’s time to decide if your expectations were met. It’s easy when they are met, you just have to enjoy it and celebrate. However, what happens when they have not been met, and your ORP “failed”?

It’s very evident that a project like this was not made for consumers. Meaning, you did not just design, build, and validate an EV conversion just to use it and call it a day. These articles are not written for this type of person. You are a tinkerer, an engineer, someone who enjoys projects. So chances are that once you build your first EV conversion, you are not satisfied. You want more power, better cooling, better wiring, more features.

The ORP is a transient idea, a temporary satisfaction you get when your ride meets your expectations, but at the same time, it is a way of quantifying what you want to do next. Enjoy these moments, building something is a matter of creativity, discipline, skill, not everyone can say they have built something like this in their lifetime.

SPARK – thoughts and conclusions

With this article we come to an end with our introductory series of EV conversion articles, where we give an overview of what it looks like, in our eyes, to convert an ICE powered vehicle into EV. This is by no means a research paper, industry standard, nor a marketing stunt to sell you something. This is an exercise in creativity, where we applied engineering knowledge, passion, and a desire to teach, for you to indulge, get your ideas going, and hopefully, get some inspiration.

This series of articles is our first full series of this blog, and through it we’ve learned and evolved our knowledge, writing, and teaching. We hope these articles serve a purpose, and we hope future articles, whether they’re part of a series or not, can spread our love for engineering and car culture in general.

As always, we’d love to hear from you, your experiences, doubts, questions or concerns. Feel free to reach out or leave a comment, and thank you!

Press clutch to shift gears – a story

April 15, 2026 No Comments

Cold air, clear skies and sunlight. My morning workout about to start, taste of cherry…

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End of Line – A story

March 15, 2026 1 Comment

Ah, the beauty of an assembly plant. Cars roll out by the minute, synchronized with…

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Boring. Dark. Cold. The industrial warehouse where we sat was furnished to resemble a corporate…

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January 31, 2026 No Comments

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It was a chilly Pennsylvania morning. Jamie was late to work again; he forgot to…

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The Integration Map will aid us in understanding how energy flows, and how information flows. Energy flow is relatively straightforward, it flows from the battery to the components that consume electricity, or from the motor back to the battery (regenerative braking). Information, though, is a different story. In this particular context, information is anything that the contorl modules might need in order to act: for example, the BMS requires temperature, voltage and current readings to determine the State of Charge. The motor controller needs to know the accelerator pedal position to determine how much torque the motor needs to make. You get the point, we need to get these components talking.

Now, there are different methods by which components could talk, mainly Decentralized and Centralized architectures. One is simpler, the other one is more powerful.

Decentralized Architecture: Simpler is Sometimes Better

Let’s start with what’s simple. Imagine throwing a small gathering. You don’t need a strict schedule or an appointed host—everyone just mingles and interacts naturally. No agenda, no coordination, everyone doing their own thing, either on their own or in small groups. A decentralized architecture works similarly: individual components communicate directly with each other without a central coordinator. This direct communication makes decentralized setups perfect for simpler, beginner-friendly EV conversions.

High Voltage (HV) Power Flow in a Decentralized Setup

Here’s what this typically looks like:

• Battery Pack → Main HV Contactor → HV Fuse → Main HV Junction Box
• From the junction box, the power splits off neatly:
  • To your motor controller and motor (for propulsion)
  • To your DC/DC converter, stepping down High Voltage to Low Voltage for your vehicle’s 12V accessories
  • To your HVAC components—cabin heater and A/C compressor

In a decentralized system, every component manages itself, simplifying the wiring significantly.

Low Voltage (LV – 12V) Power Routing

This setup remains straightforward:

12V Battery & DC/DC Converter work in tandem to power the 12V systems. The easiest way to think of this interactions is like this: the 12V battery feeds all 12V systems in the vehicle, mostly the same systems the donor vehicle had, and the DC/DC converter makes sure the 12V battery is topped off, so to speak. So to illustrate: if you were to disconnect the DC/DC converter from the 12V battery, the 12V system would still run until the 12V battery runs out. 

• Fuse & Relay Box splits power to:
  • Dashboard displays
  • Electric power steering
  • Brake vacuum pump
  • HVAC blower fan
  • Standard vehicle accessories (lights, stereo, etc.)

Communication in Decentralized Architectures

Communication is also straightforward, typically analog. The accelerator pedal sends a basic 0-5V signal directly to the motor controller. The BMS communicates battery status directly to the charger and the dash display, eliminating complexity. Charging the HV battery might be activated through manual switches. 

Pros:

• Cost-effective and beginner-friendly
• Simpler wiring, making troubleshooting easier

Cons:

• Limited expansion and advanced features
• Less precise control and diagnostics

Centralized Architecture: The VCU – Your Conversion’s Brain

Now let’s talk about centralized systems. Going back to the previous analogy, imagine this time you host a more formal and elaborate event, like a panel of experts to discuss a complex topic with a huge audience. Every expert is eager to elaborate on their point of view, every attendee is eager to bombard the panel with questions. Without an articulate, experienced host, such an event would be a mess. The facilitator needs to conduct the orchestra, so to speak, allow an expert to talk, pose a question to the audience, guide who answers the questions, etcetera. 

In EV conversions, this facilitator is called the Vehicle Control Unit (VCU). A centralized architecture introduces a VCU to manage and coordinate every aspect of your conversion, greatly enhancing your control, functionality, and safety.

High Voltage (HV) Power Flow in a Centralized Setup

The physical power routing closely mirrors the decentralized model, but each HV component now communicates its status and needs to the VCU. The VCU acts like an orchestra conductor, directing the timing and intensity of energy flow:

• The battery sends energy through a VCU-controlled HV contactor and fuse.
• The VCU instructs the inverter/controller precisely how much power the motor receives.
• The charger, DC/DC converter, and HVAC components all report their status back to the VCU, creating a comprehensive energy management system.

Low Voltage (LV – 12V) Power Routing with a VCU

The VCU oversees even the LV power flow, monitoring battery health and managing power distribution:

• DC/DC converter and 12V battery status are constantly monitored.
• Accessories and systems are intelligently managed by the VCU to optimize efficiency and reliability.

Advanced Communication in Centralized Architectures

Communication here primarily runs on a CAN bus network, a digital protocol well-suited for automotive environments:

• Accelerator pedal input first goes to the VCU, allowing intelligent interpretation of driver intentions. This allows for variable pedal maps to change vehicle behavior (like sport mode), it allows for one-pedal driving, smoother torque control, among many other things.
• The motor controller and BMS continuously relay status and health data back to the VCU in order to better manage thermal loads, durability, or safety. The battery will only allow certain amount of power to be discharged at a certain temperature and State of Charge to avoid damaging the cells long term, for example.
• Dashboard displays present centralized, comprehensive diagnostic and operational data which facilitates decision-making by the driver, or even gives insight into what to change in the VCU to improve performance or behavior.

Pros:

• Superior flexibility, scalability, and advanced diagnostic capabilities: you can start with the most basic components and then scale up, add more components or improve your calibrations to achieve the ideal vehicle behavior.
• Ability to add features like traction control, sophisticated regenerative braking, and advanced thermal management to improve safety, control and overall driving experience.

Cons:

• Higher upfront complexity and costs: in-depth knowledge of the whole system, as well as the specific VCU controls is required to achieve decent results. This is an advanced architecture that requires knowledge, time, and effort, besides it’s economic investment up front.
• Requires more initial setup time. Think of a VCU architecture like an investment: you put effort and time upfront, but you reap the benefits in the long run through a more precise, safe and tailored driving experience.

Which One Should You Choose?

To help you visualize, here’s a quick guide:

If this is your first conversion, decentralized might be your friend. This is the easiest and cheapest way to start if budget and simplicity are top priority. It will work, plain and simple. Many vehicles have been converted to EV throughout the years with a decentralized architecture, and, just like everything with EV conversions, you need to decide if it works for you based on your vehicle’s purpose. Is it the weekend cruiser for a few miles? Is it your daily? You get the point.

On the other side, VCUs are what OEMs use for a reason: they are scalable and deeply customizable. You can do almost anything you want with a proper VCU; some VCUs allow for custom code to be run, so you know your system will do exactly what you’re envisioning. 

I would not recommend a centralized architecture to a beginner due to its complexity, though. The Torque Academy’s vision of an EV Conversion is a project that is enjoyed. If the challenge is too much, it gets overwhelming.

However, if you have experience with engine tuning, car modifications, motorsports, engineering or are just deeply technical and curious, this is the way to do it. You can start with a simple battery pack, BMS and motor, adjust for them, and later on swap to a bigger motor, or bigger batteries, and adjust your VCU to match these new components. 

Wiring Best Practices (No Matter the Architecture)

Wiring is an art just as much as it is a science. In the OEM world, wiring engineers are one of the most interesting characters you can find given the nature of their craft. Everything in a modern vehicle needs to be connected to many other things, and designing these harnesses, connectors, jumpers, etcetera, is not an easy feat. For this particular reason, we will not get into details about how to design wiring harnesses or generate detailed wiring diagrams; we would need to know the specific of your design in order to properly do so. However, we can touch some of the basic points that will hopefully give you a better understanding of what wiring entails for the purpose of an EV conversion.

Regardless of your chosen architecture, here are some key best practices:

• Clearly label every wire and harness. Your future self will thank you.
• Make critical components easily accessible—think fuses, contactors, and emergency disconnects.
• Always include a High Voltage Interlock Loop (HVIL) for safety. This ensures the system won’t energize until all HV connections are safely made.
• Document your wiring clearly and thoroughly. A clear diagram is invaluable for troubleshooting and future upgrades. Which pin of module 1 goes to which pin of module 2? Which wire of sensor A goes into which pin of module 4? All of these details need to be clearly labeled and documented for future reference!

Common Pitfalls (and How to Avoid Them)

• Poor grounding: Always ensure proper chassis grounds. Bad grounds cause strange, elusive issues. It’s better to get grounding right at the beginning. Clean terminals, ensure contact between metal is sufficient, confirm continuity to ground, etcetera.
• Mixing analog and digital signals improperly: Separate or shield wiring to avoid interference. Keep in mind that analog signals are low voltage low current signals, and any high voltage or high current wiring nearby could induce a current. Shielding is key: look for industry specifications and follow them. Someone has already gone through this and documented it, use those specifications!
• Undersizing wires or fuses: When in doubt, go one size bigger. You wouldn’t want a fuse, let alone a wire, melting during normal vehicle operation due to normal current. Research and use industry specifications.
• Inaccessible wiring or fuses: Make serviceability a design priority. Imagine you keep blowing a fuse and the only way to get to it is to remove the HV battery pack from the vehicle. Not our definition of serviceability. 

Bringing it All Together

Your choice between centralized and decentralized wiring architectures comes down to your project’s complexity, your comfort level with technology, and your future ambitions. The decentralized architecture is beginner-friendly, cost-effective, and simpler overall. Centralized architecture, with a VCU, offers more sophisticated management, flexibility, and advanced diagnostic capabilities.

Remember, neither choice is inherently superior—they simply fit different scenarios. Understanding your needs clearly is the most important step. We sound like broken records, but keep going back to your Engineering Decisions, make sure what you decide to use for your conversion matches your vehicles design intentions, budget, and interest. 

The SPARK methodology’s Route phase is about clarity and confidence. Whether you choose decentralized simplicity or centralized sophistication, make your decisions deliberate. Soon enough, you’ll be ready to move into the Kickoff phase, turning your carefully planned wiring into a live, working EV.

Feel ready to start wiring your conversion? Have any lingering questions or insights from your projects? Share them—we’d love to hear your stories and challenges, and we’re sure the community will too. Let’s keep the conversation going and our projects moving forward!

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Let’s explore how charging equipment and auxiliary systems form the hidden backbone of your EV conversion, making it not only operational but also enjoyable to drive.

Charging Equipment—Giving Your EV Life

What is EV Charging Equipment?

Arguably one of the most contentious topics in today’s automotive industry, EV charging is not as simple as it sounds. Luckily, it’s not as complex as some people think, either. What makes it complex, though, is the comparison one tends to make between refueling a gasoline or diesel powered vehicle and charging an EV. There’s no “slow fueling” an ICE vehicle, nor is there “fast fueling” for that matter, but those concepts do apply for charging an EV. 

But none of those comparison or concepts matter to your EV conversion: you need to make sure your charging is as fast as you need it to be. Your requirements for this will depend on your Engineering Decisions, and your Component Strategy (battery pack selection specifically). 

How so? Well, your battery pack will dictate the voltage your charging equipment will need to provide, as well as the total energy it can hold and how fast it can accept it. Your Engineering Decisions will dictate the range and expected use for this vehicle. It’s not the same thing to have to charge your conversion for a Cars and Coffee event 15 miles away on Saturdays during the summer, than to have to charge your daily driver for an 80 mile round trip every day, even during winter. Charging time matters!

On-Board Charging Module (OBCM)

The On-Board Charging Module (OBCM) might not be the flashiest part of your EV conversion, but it plays a pivotal role in making your build practical and enjoyable for everyday use. Think of the OBCM as the bridge connecting your home’s electrical supply (AC power) to your battery pack (which needs DC power). It’s essentially a smart transformer, converting alternating current (AC) from your house into direct current (DC) that your batteries can store. Choosing the right OBCM isn’t complicated, but it requires attention to a few key specs: voltage, current, power rating (measured in kilowatts or kW), and efficiency.

The voltage rating of your charger must match your battery pack’s nominal voltage—whether that’s 96V, 144V, or even higher. Some chargers have programmable output voltage within a certain range, some don’t, so make sure to check with the manufacturer of your part before making any purchase! Next up is power output, typically ranging from about 3kW for smaller, basic conversions to 22kW for high-performance setups. This rating directly impacts how quickly your battery can charge.

Here’s a quick, practical example: if your battery pack has a capacity of 30kWh and you pick a common Level 2 charger rated at 6.6kW, charging your battery from empty (0%) to full (100%) would theoretically take about 4.5 hours (30kWh ÷ 6.6kW ≈ 4.5 hours). Realistically, add around 10-15% extra time due to efficiency losses, meaning you’ll be plugged in for about 5 hours. Efficiency is crucial—it dictates how much of the electricity from your wall actually makes it into your battery pack, and how much gets lost as heat.

When selecting an OBCM, carefully review its specifications and compatibility with your chosen battery chemistry and voltage range. Also, consider the available electrical supply at your home or workshop: a more powerful charger might require a dedicated circuit or even an upgrade to your electrical panel. Make sure to pick a reliable brand—saving a few bucks upfront on a cheap charger may mean dealing with headaches down the road. Remember, your OBCM is part of your EV, not your at-home charger, so if it doesn’t work well, it won’t work well in ANY charging station you try. This is a component that will significantly affect your EV’s usability, charging convenience, and ultimately your satisfaction with the project.

Off-board Charging Stations

While your On-Board Charging Module (OBCM) plays a vital role converting household AC power into DC for your battery pack, it’s the external charging station that will shape your day-to-day experience. Understanding these chargers is straightforward, but selecting the right one involves balancing convenience, charging speed, complexity, and of course, your budget.

First, we have Level 1 charging, which is essentially plugging your EV into a regular 120V household outlet. Think of this as the slow cooker of EV charging: convenient, low-cost, but it takes time. Lots of time. A typical Level 1 setup provides around 1 kW, meaning a modest 30 kWh battery pack could take nearly 35 hours to fully charge. If your converted EV is just a weekend cruiser or you drive fewer than 30-40 miles per day, this slow and steady approach might be more than enough, especially since you’re charging overnight anyway. No extra installation, minimal complexity, and it won’t break the bank—just plug it in overnight, and your EV will be ready for another day around town.

But let’s say your EV sees more use—maybe it’s your daily driver or your weekend warrior, and you want faster, more convenient charging. That’s where Level 2 chargers come into play. Operating on 240V power (like your clothes dryer or electric oven), Level 2 charging systems can deliver anywhere from about 3.3 kW up to 22 kW, though most DIY conversions stick to something around 6.6 kW. Continuing our earlier example, with a 30 kWh battery and a 6.6 kW charger, you’re looking at roughly 4-6 hours to go from nearly empty to fully charged. The biggest upside here? Convenience. If you install a Level 2 charger at home, every morning you’ll wake up to a full battery without the hassle of extended waiting periods. Sure, installation requires a bit more upfront investment—think dedicated 240V wiring and potentially a professional electrician—but if your EV is part of your daily routine, the cost is well worth the investment. Keep in mind, however, that your Level 2 charging station does not define the charging speed of your battery, that’s the OBCM. If the OBCM is rated at 3.3kW, for example, and your Level 2 charging station is rated at 12kW, it won’t charge the battery at 12kW, it will charge at 3.3kW. On the flipside, if your Level 2 charger is rated at less power than your OBCM, then your battery charging power will be limited by the charging station. It’s recommended that your Level 2 charging station power matches or exceeds that of your OBCM. 

Finally, let’s talk about DC Fast Charging (Level 3+ charging)—the powerhouse of the EV charging world. If Level 1 was your slow cooker, DC Fast Charging is your microwave: blazing fast, super convenient, but a bit more complicated and costly. A DC fast charger bypasses the OBCM entirely and sends high-voltage DC directly into your battery pack, charging it from nearly empty to 80% in as little as 20-30 minutes. But there’s a catch: not every battery pack or EV system can handle such rapid charging without specialized (and often expensive) battery management systems. For most DIYers, incorporating DC fast charging is a significant leap in complexity and budget—typically involving advanced battery management systems (BMS), thermal management solutions, and ensuring your battery cells can handle rapid charging rates safely. The DC Fast Charging station should also communicate with your BMS and sometimes your EVCU, or Electric Vehicle Control Unit (if equipped), in order to allow charging. Some DC Fast Charging brands, like EVGo, have recently banned EV conversions from using their charging network (https://cleantechnica.com/2025/03/13/evgo-no-third-party-adapters-or-ev-conversions-allowed/)

When selecting your charging solution, think carefully about your actual needs, budget, and how you plan to use your EV. For most DIY conversions, Level 2 charging hits the sweet spot of practicality and affordability. However, if your conversion is your dream road-trip machine or a long-distance cruiser, investing extra resources into DC fast-charging capabilities might make sense. On the other hand, if simplicity and affordability are your top priorities, Level 1 could serve you perfectly. Like everything in automotive engineering—and in life—it’s all about balancing your goals, budget, and a sprinkle of common sense.

Selecting Your Charging Equipment

Now that we’ve covered the basics, let’s sum them all up in a very quick and concise step-by-step protocol.

Step 1: Determine OBCM output voltage and power

Assuming your battery pack has a nominal voltage of 96V, your OBCM should be slightly above this. Most OBCMs aimed at EVs are rated for nominal battery pack voltages, so look for one that matches your pack: it should be able to output a slightly higher voltage in order to charge it (remember current flows from higher voltage to lower voltage, so if both the battery and the OBCM were exactly at 96V, the current flow will be minimal. The charger needs to have a slightly higher output voltage!). 

Step 2: Determine your charging speed (OBCM power rating)

Now, power is relatively easy to select given the fact that most OBCMs are rated at 3.3kW, 6.6kW, 7.6kW or 11.6kW, give or take. If you are looking for the cheapest component, go for the lowest power rating. If you’re looking for the fastest charging time, go for the highest power rating. 

But if you’re into doing some math, let’s do a quick calculation:

Assuming your battery pack has 30kWh of usable energy, and you want to charge from 0% to 100% (not recommended, as mentioned in our article about battery packs, but makes math simple here) in 4 hours. That means 30kWh ÷ 4 hrs = 7.5 kW of OBCM power output is what you need. Need something faster? Go as high a power rating as you can get! 

Step 3: Check charger efficiency and compatibility

Make sure your charger exceeds at least 90% efficiency. Rememeber, the less efficiency, the more heat is generated, and that’s lost energy and time! Also compatibility: is your OBCM compatible with your CAN network (if your conversion has one)? Are your connectors the right ones? Is it programmable or does it need a ‘master controller’ to dictate what it does? 

Auxiliary Systems—More Than Just Extras

Auxiliary systems maintain vehicle functionality and comfort, and neglecting them can turn a well-executed conversion into an inconvenient or unsafe ride. I’d like to bring your attention back to our first article of this series, were we laid out our theory of EV conversions in the modern era as enjoyable expressions of engineering, more so than A-to-B basic transportation. Under this premise, it is absolutely paramount that driving this hypothetical machine is an enjoyable experience, whatever that means to you. If you feel like you need Air Conditioning, a good sound system, power steering and a big screen to enjoy this hypothetical EV conversion, then, by all means, please plan for it. On the flip side if you think you need nothing but pedals, a steering wheel and something reminiscent of a seat, that’s what you should get. But above all, consider safety!

With that editorial out of the way, let’s get into what Auxiliary Systems are, and what you might need them for.

Essential Auxiliary Systems

The full functionality, outside of just powering the wheels for motion, of any EV requires the following components:

• DC-DC Converter: this acts like the alternator of an ICE-powered vehicle; it feeds all low voltage electrical systems.
• Brake Vacuum Pump: this gives power to your brakes so you can easily actuate them through the brake pedal.
• Power Steering System: this system allows for easy manipulation of the steering wheel to change direction of the car while driving.
• Air Conditioning (A/C) system: this conditions the air in the cabin to allow for a more comfortable driving experience. This includes heating and cooling. 

DC-DC Converter: Powering the Essentials

The DC-DC converter is your EV conversion’s equivalent of an alternator—except, instead of being belt-driven by an engine, it converts the high-voltage DC from your battery pack down to a stable 12 volts to power your vehicle’s accessories. Everything from your lights, radio, gauges, to wipers relies on this converter.

Selecting the right DC-DC converter involves looking at two main things: power rating and efficiency. Typical DIY conversions use converters rated between 500W and 3000W, depending on how many accessories your vehicle has. If you’re running basic electronics, a smaller 500–1000W converter might suffice. However, if your build includes powerful audio equipment, electric power steering, or multiple accessories, you’ll want something closer to 1500–3000W. Efficiency matters too, since wasted energy turns into heat, reducing your overall driving range and potentially causing thermal management headaches. Aim for converters with efficiency ratings of 90% or higher to keep things cool and efficient under the hood.

Brake Vacuum Pump: Keeping Your Brakes Safe

When you remove the internal combustion engine from your donor vehicle, you’re also removing its built-in vacuum source, which your brakes depend on for power assistance. Without vacuum, pressing the brake pedal can feel like trying to squeeze a brick—definitely not safe, and certainly not enjoyable. That’s where a brake vacuum pump steps in, providing consistent vacuum pressure to your brake booster to maintain that smooth and responsive brake feel you’ve come to expect.

Selecting a vacuum pump for your EV conversion isn’t too complicated, but it does require a bit of thought. Typically, automotive brake systems need a vacuum level of about 18–25 inches of mercury (Hg) and a flow rate of around 1.5–3 cubic feet per minute (CFM). For most conversions, you can keep it simple and reliable by using a vacuum pump from an existing EV or hybrid car with similar brake booster size and weight characteristics—think of a Chevrolet Volt, Nissan Leaf, or even a Tesla Model 3. These are readily available second-hand, proven to work well, and generally affordable.

If you’d prefer doing it by the numbers or you’re tackling a less common vehicle, start by consulting your donor vehicle’s service manual to determine the original vacuum level and booster size. No manual? No worries. A quick test with a vacuum gauge on the booster of a similar-sized vehicle can give you a solid benchmark. Once you’ve got your target vacuum level, match it with a vacuum pump that meets or slightly exceeds this requirement. It’s always safer—and smarter—to have a bit more vacuum and flow capacity than you think you’ll need, ensuring reliable braking power even under heavy or repeated braking conditions.

Remember, your EV conversion isn’t just about speed and range; safety and driveability matter just as much. Don’t skimp on your brake vacuum pump—your stopping power literally depends on it!

Power Steering System

When selecting a power steering system for your EV conversion, the simplest, most straightforward solution is to keep your original hydraulically-assisted steering rack and just swap the engine-driven hydraulic pump for an electric-powered hydraulic pump. This solution avoids the hassle of replacing your steering rack entirely and ensures compatibility with your vehicle’s existing steering geometry. You can easily source second-hand electric hydraulic pumps from vehicles like the Toyota MR2, Volvo S40, or certain European vehicles that came with electro-hydraulic setups.

As an alternative—though admittedly a bit more complex—you might consider swapping in a fully electric power steering rack or assist-column system from a similar-sized EV or hybrid vehicle like a Chevy Bolt or Toyota Prius. This option eliminates hydraulics entirely, reducing complexity and maintenance. Whichever route you take, keep in mind critical factors like vehicle weight, tire width, and desired steering effort to ensure the selected system has enough power and responsiveness. Also, don’t overlook the electrical power demands of your setup—bigger pumps or fully electric racks require higher current, which could impact your range and battery sizing. Always choose slightly more capacity than you initially calculate, especially if your build involves performance driving or larger-than-stock tires.

HVAC Systems (A/C Compressor and Coolant Heater)

In your EV conversion, comfort isn’t a luxury—it’s essential. Without the heat from a gasoline engine, your car will need fully electric HVAC components, including an electric compressor for air conditioning and an electric coolant heater for warming up the cabin.

A/C compressors: In EV conversions, the electric compressor typically integrates directly into your original A/C system, leveraging existing hoses, the evaporator, and condenser. Usually, minimal modification is required, making installation relatively straightforward.

Coolant heaters: These units usually heat up the heater core circuit, which the majority of modern donor cars already have, and will require a small coolant pump to circulate the warm fluid across it. 

Selecting these components starts with understanding your needs: consider your vehicle’s interior size, typical passenger count, and climate conditions. If you’re building a small weekend cruiser and live somewhere temperate, you probably won’t need a powerful compressor or heater. However, if your EV is your daily driver in extreme climates—hot or cold—you’ll need more robust systems. Most DIYers keep things straightforward by sourcing second-hand electric compressors and coolant heaters from factory EVs or hybrids, since they’re already proven reliable and sized for typical passenger car cabins. As with all the other auxiliary systems, always choose slightly higher capacity than your initial calculation suggests; it’s better to have a bit more power available, ensuring you’re comfortable and your EV conversion remains enjoyable year-round.

Calculating Auxiliary Loads

So after all these systems have been added, your electrical needs have changed. You now need to know what the peak power consumption is (in kW) for each component, and every other component that was alrady in the donor car. Lights, power windows, screens, you name: if it uses electricity you should be able to at least estimate its power consumption. This will dictate 2 main things. 1) your DC-DC converter rating and 2) the impact these component might have in your range when in use!

Quick Summary of Auxiliary Systems

Conclusion: Charging Ahead with Confidence

Selecting charging equipment and auxiliary systems might not feel as exciting as choosing your motor or battery pack, but it’s every bit as crucial—and rewarding—in the long run. These choices impact not just your EV’s usability but its personality too. Remember, your EV conversion is an expression of both engineering and creativity, and thoughtful decisions here ensure your build is safe, reliable, and enjoyable to drive. Up next, we’ll move into the wiring and cooling systems, tying everything together and inching closer to hitting the road in your electric dream machine.

Join the conversation: share your thoughts, ask questions, or tell us about your EV conversion journey or plans in the comments below. We’d love to answer any questions we can and/or learn from your experience.

Press clutch to shift gears – a story

April 15, 2026 No Comments

Cold air, clear skies and sunlight. My morning workout about to start, taste of cherry…

Read More

End of Line – A story

March 15, 2026 1 Comment

Ah, the beauty of an assembly plant. Cars roll out by the minute, synchronized with…

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PLAN – Designing an EV conversion from scratch: a SPARK walk through

March 1, 2026 No Comments

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February 14, 2026 No Comments

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