How to build your own electric car for £10,000
During the week, Tom Cheesewright advises the likes of Nasa. Weekends, though, are more down to earth: scavenging car breakers’ yards and trawling the internet looking for discarded first-generation hybrid electric car parts.
It’s because he’s building an electric vehicle (EV) on his drive in a Manchester suburb, and fabricating parts for it in a back garden tent.
This is his second attempt at building an EV that resembles a classic car, and both have been constructed around the same MOT-failure BMW Z3 two-seater from 1999.
The first, which retained the Z3’s bodywork, had a 20-mile range and was used for local trips to shops and schools.
The second, pictured here, is upgraded, has a slightly better range and looks very different – with the Z3 chassis shrouded in a 1950s-style sports car body.
Self-confessed petrolhead Cheesewright, 45, sparked into action during lockdown in 2020: “I was looking at classic cars on YouTube and my kids got excited by the prospect of whether we could have one,” he said.
“But everything they wanted was £500,000, so I said no, but maybe we can make one. So the idea came about, OK, let’s buy an old convertible, convert it to electric and see if we can make it look like something from the 1950s.
“There was also the professional angle: I do a lot of work consulting around the future of transport for organisations like Nasa and some of the big car manufacturers.
“I wanted to understand EVs deep down. What’s better than getting hands-on?”
So he started the scavenge: an electric motor came from eBay, which he found he could make work after acquiring an inverter, a piece of equipment that allows the batteries to power the motor. They – he and his kids – then started acquiring all the other necessary parts, as Cheesewright educated himself on precisely what was required to build an EV.
He discovered that regulations meant the base car had to be pre-2001, otherwise he wouldn’t be able to get it approved for road use if he swapped the original petrol engine for electrical power.
“We settled on a BMW Z3, found a 1999 MOT-failure for £800, then pulled it apart and recouped some money by selling things like the engine and catalytic converter, making around £300,” he said.
Which you might consider to be a drop in the ocean of the cost of building a DIY EV. Also, parts were surprisingly inexpensive: the batteries cost £800, the charger £100, junction box £200, inverter £20, the motor £200. Two junction boxes cost £100, and cabling £350.
The electronic “brain” of the new powertrain came from software specialist EV BMW, one of the many members of the EV geek community who exchange learning and expertise. It attaches to the inverter and controls power distribution. That control board cost £400.
Cheesewright fabricated various components to connect the motor, gearbox and back axle. He had most of the right tools, but bought a lathe for £600 to machine parts, then resuscitated welding equipment that had been discarded by a local garage.
Non-EV parts included a £40 Vauxhall power steering pump, £40 Audi brake boost vacuum pump and a battery box made from an old washing machine.
“Not all car recyclers are yet up to speed with EVs, so some parts are incorrectly described - inverters and batteries get confused, for instance,” said Cheesewright. “Some parts are overpriced, some underpriced, so it’s a mix of grabbing bargains or letting pieces sit on shelves unsold until realistic offers are accepted.
“Then go to the EV community forums: you’ll find someone’s got such-and-such a part working – and they’ll share how they did it. There’s hundreds in the community, from people pulling things together in their back garden to people with great facilities producing beautiful EVs.”
Cheesewright has a degree in mechatronic engineering, which means, essentially, that if something is electrical or mechanical, he can fix it, make it, install it and connect it to something it hadn’t necessarily been designed to connect to.
That’s just as well, because his garden-build EV features batteries from a BMW 330e, the electric motor and battery charger from a Mitsubishi Outlander PHEV, electrical current inverter from a Toyota Prius, as well as a heater from the Mitsubishi to replace the BMW’s engine-warmed unit, along with a high-voltage junction box from a local electrical supplier.
The power, an electrical equivalent of the BMW’s original 140bhp, finds its way to the road via the BMW’s original gearbox and rear axle.
“This is kind of what I qualified to do” he said. “I never worked as a professional engineer and I did that degree 25 years ago, so a lot of it has gone from my head. Most stuff I’ve learned recently is either through help from the community or from watching YouTube videos.
“I’m quite good at hardware design, so I’ve shared my designs for 3D-printed parts that other people now use. That’s really satisfying.”
The second iteration of Cheesewright’s DIY EV is close to road-readiness. A two-and-a-half-hour charge from a domestic electricity supply will provide about 25 miles of range, a distance that’s ideal for pottering locally. Judging by the first version, it should easily pass an MOT roadworthiness inspection.
It looks very different from a Z3. The body is a Tribute Automotive Z300S, which is inspired by swooping 1950s Maseratis. It cost £3,180.
“You don’t have to be a super genius to do this,” said Cheesewright. “I’m certainly not. If you’re willing to be patient, to listen to advice and learn, and if you like learning from your mistakes, then I’d say do it. Even without a garage or any really great tools or materials, you can do this.
“Most people doing this have one of three skill sets: they understand mechanics, they have fabrication skills, or they are software nerds or come from an electronics background and understand power electronics.
“If you’ve got one of those three and you’re willing to learn, then it’s eminently achievable.”
And he didn’t say: “It’s not rocket science” once...
