Article

What to Expect Doing an EV Conversion on Your Own

Ben Parker

Paul Dexter's BMW 1974 CS converted to become the "CSE". This BMW has been given new life with a large Tesla drive unit giving it almost 500hp.

Credit Paul Dexter

Article Highlights

Although electric vehicle conversions are becoming increasingly popular, they still (for the most part) have only been achieved by hobbyists, engineers, and madmen. For many of us laypeople, the idea of embarking on that level of a project can seem exciting, and altogether daunting. I’m really not anything close to an engineer, I can fumble my way through most technical things but have little to no knowledge about many of the intricacies of electrical engineering, or mechanical engineering. So I rely on the knowledge and expertise of others. Enter Paul Dexter, who I virtually spoke with to help answer some of these questions.


Over the past two years as I've more seriously considered doing an EV conversion myself I've realized those that actually complete one, have a high level of chutzpah and commitment. After having a conversation with Paul it seems he’s got the chutzpah and the commitment. From my virtual conversation with Paul, and after reading a few of his build blog you can see that Paul is a smart guy who’ll sign himself up for challenges, and crush them. Paul is an entrepreneur, with a background in making theatrical AV systems. 


Why should you convert your car to electric?


After owning and driving an early Tesla Model S Paul said “I’ll never drive a gas car again.” it didn’t take long for Paul to miss his classic European cars and desire to blend the two together. What he didn’t know at the time was that it wouldn’t be at least two years until the journey was close to being over. This was something that Paul reiterated to me a few times. “I had no idea it’d be two years and I’d still be working on it I figured I’d be driving it in a year. Doing a project like this, it’s very hard to go back especially when you do it with Tesla components, I had to keep going, I printed out a ‘just keep going’ poster with a mockup of what the car was gonna look like. Just to keep me motivated.”


Choosing the right car to convert to electric


The most common electric vehicle conversions are cheap cars, using, lead-acid or other low cost, low efficiency batteries attached to the existing transmission. You can see pictures of Toyota Camrys with the whole engine bay filled with batteries, or trucks with the bed filled with batteries. Although these have some definite merit of their own, some people may want something more interesting. 


When choosing the right car for an electric vehicle conversion there are a few considerations to make. What are your goals with the car? Do you want it to be fast? Is it gonna just be a grocery getter or do you want something with a longer range? These are all questions to ask when you’re considering the final car for the project. 


For Paul, a car that had power, long-range, and that he could still drive his kids to school in. That was the criteria, which led him to the BMW CSI. Paul was able to get a body for a good price but that needed a considerable amount of bodywork to restore all the rust, in Paul’s words “these [cars] are basically built to catch and hold rain. This one had tons of rust, a horrendous amount of rust. The first year of the build was just the restoration of the car.” 


This is definitely something to consider as well when you’re picking a car to convert. What kind of work does the car need to get it to completion? For Paul, the challenge was worth it. I’d agree with him he’s really brought new life to this car in so many ways. This theoretically will increase the resell value of the car if he ever decides to sell it because it’s not only a full restoration, but it’s now electric.


A picture of the 1974 CS before the electric motor swap, when Paul picked it up it was in fairly good condition. Except for the massive amounts of rust that would need a ton of fabrication and restoration work.

Credit Paul Dexter

Here's a picture of the Tesla drive unit going into the rear of the CSE which had to be retrofitted with a few mounts in the rear. Paul also used a variety of custom-fabricated parts, mounts and custom axles.

Credit Paul Dexter

“So I eventually just said I need to do a Tesla, that’s what I’ve driven, that's what I love."

What do you need to know before starting an electric vehicle conversion?


I’m not a mechanic or an engineer, can I do an electric vehicle conversion on my own? Well, the short answer is probably, no. But it’s not that simple, this is a pretty complicated project and it does require knowledge and or guidance. For Paul who works by day as an AV specialist, he was able to leverage some of his warehouse space to put in a lift, and use some of his electrical wiring knowledge. Along the way he met a buddy who became inspired to convert an E9 to electric so the two of them swapped knowledge and were able to help each other in a sort of symbiotic relationship. This is really what it will require if you’re trying to embark on a project like this. Find people near you who may be able to fill in the knowledge gaps that you don’t have. 


There are a lot of resources on the internet, but it may take some time to find specifically what you need. For Paul, he started looking at some of the DIY electric vehicle conversion forums and found it was hard to find productive feedback from people on the forum. It wasn’t until he found a BMW E9 restoration forum that he was able to get some actual productive feedback. 


Identify all the parts of the conversion process that you can do yourself, look for people in your network who can advise or help on the other parts, then if nothing else hire out anything leftover. 


What parts do you need for an electric vehicle conversion?


It all depends on what you want out of the car. I asked Paul about all of the components going into the CSE and here’s what he said, 


“I considered doing a low voltage conversion you know for $10,000 in parts or less.. But with one of those DC 24 volt motors, they’re 50 to 100 hundred horsepower, you still have to shift, you’ve got that heavy transmission and differential so you’re wasting a lot of efficiencies. So I eventually just said I need to do a Tesla, that’s what I’ve driven that’s what I love.”


So the CSE has a Tesla large drive unit. 14 Tesla modules to give 320 volts. Using a Tesla DC-DC converter to convert that 300 to 12 volt DC to run the 12V systems. He’s using the Tesla drive unit that has the inverter to the AC motor built into it using an 057 controller. Using a Bosch pump through a Kawasaki 1000 radiator motorcycle radiator intercooler pump it passes through the drive unit, the 12-volt converter, and then ultimately back through the Tesla charger. 


With all that Paul expects a 240-mile range. The BMW is much lighter than the Tesla but still less aerodynamic than Tesla. An estimated 480hp with a crazy amount of torque. Which is more than any BMW CSI or CSL has ever had. This thing is going to be nuts.


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Paul also created a digital dash for the car using Raspberry Pi

Credit Paul Dexter

“The world needs more people to try it even if they fail”

The final details


One of the things I love so much about this build is that Paul has put some work into the details of the car. If you check out his blog you’ll notice that he’s made his own digital dash that runs off of a Raspberry Pi. This is actually exactly what I’ve wanted to do with my car so I was excited to see someone else actually succeed in making this happen on a circular display. You can see on Paul’s blog the mockup of what this thing will look like when it’s all done and it’s great. 


What you should know before converting your car from gas to electric?


You should know that each of these builds is so bespoke, there’s more than one way to slice a pie and you really can make whatever you want out of it. Paul’s BMW CSE is really going to be something special, and it’s completely different than Jim Belosic’s Hondaru. So understand that your path to converting the car may be wildly different. 


When I asked Paul what advice he had for anyone he expressed “The biggest thing is, I’ve seen a lot of people try but not make it. My biggest advice is to make sure you’re ready for the long haul. Assume it’s going to take a couple of years or more. Be ready to double your budget.


The battery box fitted into the engine bay with some nice logo details.

Credit Paul Dexter

Conclusion 


It’s difficult and very daunting to consider doing an electric vehicle conversion, but luckily there’s a lot of other people crazy enough to try one that you can probably get a good amount of help along the way. As Paul put it, “The world needs more people to try it even if they fail”. The more people who step up to the challenge the more each of us can help each other do it. 


If you’re considering doing an electric vehicle conversion here are a few places you can start to get some ideas from:


Paul’s BMW CSE Build Blog


DIY Electric Cars


Build Your Own Electric Vehicle (Book)


Convert It! (Book)