So, I’ve been working on my project for about 3 years, and thinking about it for much longer.
I’m converting a 2012 Caterham Seven to be an EV.
The project car was bought in 2022 as an unregistered ex-drift car - used for drift experiences and training people to drift. The car was in good mechanical shape but the bodywork had seen better days. This particular car was a 1.6L Ford Sigma based “SV” version of a Seven. The SV mean “Series Five” which is a 100mm wider than what most people would consider a standard, or S3 chassis’ed Seven. The extra width was a purchase requirement to give me more room for batteries.
I’m a semi-retired electronics and software engineer. Graduated in electronics and silicon design in 1989 and have run (by myself and with others) a succession of electronics and software product companies, some of which were listed on the London Stock Exchange (though that seems like a long time ago now!
). Most recently, as well as running my own company, I was CTO of a Californian tech company that produced video communications services for people who are deaf and use sign language, we employed about 2,500 interpreters and ran over 40 call centres. I’ve also sat on a number of ITU and similar standards committees. So, the first task I had was to get the car road registered in the UK. The theory being that it would be easier to get DVLA re-registration from a road legal ICE car rather than going straight to an EV conversion first and then having to get a road registration essentially “as new” as an EV. We’ll have to see if that works out.
So the car was made road legal in early 2023 (after a bit of back and forth with DVLA, of course) at which point I stripped the engine and gearbox out and sold them. The car was then 3D scanned and I started to work out what would fit.
Since then I’ve been looking at conversion options. The “volume” available in a Seven is extremely restricted and I decided I probably couldn’t take a pre-owned second hand drive unit and fit it in my car.
I should say at this point that my motivation is to show a conversion can be done with a Caterham and that it can deliver a fun EV version of a classic sports car. I helped run the Caterham and Lotus Seven club for 3 years and I’m still the coordinator of the EV Special Interest Group for the club. I’ve published a number of articles in the Club magazine about this project.
I am also thinking this could be a business if it can be made to be viable. I am environmentally concerned and have home solar (20 years) and a Tesla battery (5 years). We also drive an ID3 (took delivery on the first day they were available in the UK
). I am in the fortunate position to be able to run this conversion through my company and to spend “appropriately” to get a prototype running. It can be “cost reduced” later.Back to the car.
I’ve looked at a number of motor/inverter options and spent about a year working with a local motor supplier. But in the end it didn’t work out with them. They wanted too much money to integrate a motor and inverter together and so I started looking elsewhere about a year ago.
Since then I’ve landed on Helix as a motor/inverter provider and I hope to take delivery of both in a few weeks.
The other key part of my project is the sports car bit. I want it to eventually have the same sort of performance as a Caterham (my other Caterham is a 420 version - 210bhp and 200Nm, 0-62mph in about 3.8s, that I built in 2017). So I need about 150kW of motor and enough battery to feed it. That has led me to an architecture that’s probably a bit different (though probably not so much on these forums
): 800V motor, silicon carbide inverter, 600A, 220V battery pack and a 200kW DC2DC converter. Is this unique… possibly ¯\_(ツ)_/¯ . So the DC2DC converter allows me to use a battery pack that can be switched around and to just reprogram the DC2DC converter to step it up to the 800V needed by the inverter/motor. It’s an extravagance… I know! But it means I can have a 220V battery pack that will fit in the car instead of having to try and get to a minimum of 400V and actually 800V for the motor I’ve gone with.The Helix motor is very compact, at 200mm diameter, and will fit in the transmission tunnel where the gearbox would normally fit. This also gives me more battery space in the front of the vehicle. I’ll also have a couple of modules in the rear where the fuel tank used to sit.
What else… I’m also planning to use DC charging (FOCCCI arrived today - yay) and hopefully not have an AC charging option (to save space and weight). At least not AC in the car… I’ll probably have an external AC to DC charger that sits at home. Talking of weight, the spreadsheets are telling me it’ll be just over 600kg (original car was 540kg), so probably more like 650kg I expect in the end.
You can see some blog posts about the project on my Blog at https://purplemeanie.co.uk or I’ve done a few YouTubes at https://youtube.com/c/purplemeanie. I have video and stills from the last two years that I’m working on publishing in the next few months.
Happy to take flak and answer questions
John
). If you manage to govern regen, you can govern charging with the same numbers. I don't see a need to alter Foccci code as that also cuts you off from future development.
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