Your questions answered

Electric-car conversions: can I build my own electric car?

The idea of carrying out your own electric-car conversion seems tempting, but you’ll need specialist knowledge and it won't be cheap

Electric car conversion

Electric-car enthusiasts have been building vehicles at home for years with varying degrees of success. Those bitten by the home-built EV bug include such luminaries as Mate Rimac, whose early efforts to electrify a BMW 3 Series for rapid acceleration were the springboard to a now-significant role in the global electric-car business. While some appreciate preposterous acceleration, others have been enticed by the prospect of low running costs and zero tailpipe emissions, but until the advent of a mainstream electric-car industry churning out mass-produced motors, batteries and controllers, home-builds tended to be something of a niche interest. Nowadays though, you can pick up EV components pretty easily from a range of sources that have sprung up to service demand from global carmakers, and there are enough old electric cars around to make repurposing their used batteries a viable option, too.

As the switchover to new EVs gathers pace, demonstrated by recent sales figures there’s another trend emerging rapidly alongside it. It’s spearheaded by a raft of businesses set up to convert classic and older internal-combustion cars to electric power, either as turnkey restored models or by providing kits of parts for keen DIYers to fit at home in the garage.

While the price of new EVs is coming down, price is still a major obstacle for many drivers who want to make the change to electric power. It’s the same story in the conversion market, too, which so far seems focused on expensive restorations rather than helping EV hot-rodders build projects on a shoestring. How expensive? It’s a tricky question, because so much depends on the amount of traditional work required to revitalise a classic – renewing the body and upholstery for instance – and that’s on top of buying it in the first place. Once you’ve factored in engineering, electronics and batteries, suffice to say a turnkey conversion is likely to cost anything from around £30,000 for a classic Mini to hundreds of thousands for something more exotic. As the new market changes, however, there have been some excellent and slightly more affordable electric cars launched recently. But if a Renault Twizy or SEAT Mii electric isn't quite for you, then what are your options? An electric conversion could be your answer. You might have seen some of the incredible classic-car conversions unveiled recently, from the likes of Electrogenic and Lunaz. And if they can make an electric Aston Martin DB6, surely lots of people could be doing this themselves?

Not exactly. While it has been done and there are companies out there doing it, a full and proper electric-car conversion is the kind of project you should only take on if you have an in-depth understanding of automotive and electrical engineering.

In other words, if you’re reading this article in order to find out how to do an electric-car conversion, then they probably aren’t the kind of thing you should consider doing yourself. Nonetheless, the process of taking an internal-combustion-engined vehicle and turning it into a greener electric car is interesting and not impossible for individuals with the requisite skills.

Electric-car conversions: how do they work?

First, you need to find a car to start with. Something light is ideal, as extra weight will make your electric car slower while reducing its range. Ideally, you also need something that doesn’t have power steering or power-assisted brakes, as these are powered by the engine.

Then you need to strip out anything fuel-related: that means getting rid of the fuel tank, the exhaust, the engine, the starter motor, the radiator, the coolant tank, the fuel lines and several other components besides.

Keep hold of the transmission, though: you’ll need this to direct the power from an electric motor (these can be bought fairly cheaply on the secondhand market) to the wheels. You’ll also need to make an ‘adaptor plate’ to line up the motor and the transmission, and source a ‘coupler’ to connect the motor’s rotary power to the transmission.

Then you’ll need to get hold of some battery cells. A handful of 12v batteries will do, or you could investigate taking a ready-made battery from a cheap used electric car, such as a Nissan Leaf or Renault ZOE. Bear in mind that – like all of the other components – these need to be anchored securely in place.

Another key component is a controller: this controls the power running between the batteries and the electric motor. The higher the amperage, the faster and more efficient your converted electric car will be, so buy the best one you can afford.

Those are the main considerations. If you’re likely to drive when it’s cold, you may want to consider how to make up for the lack of a heater, which in a normal car uses excess engine heat to keep the interior warm when required. Without an engine, you’ll need to find another solution for this.

Swindon Powertrain Classic Mini Kit

Can I buy an electric-car conversion kit?

If you need to source parts, there are companies that provide a full set of everything that you’ll need. For example, the website has a range of electric-car conversion kits suited for different-sized cars: these start from around £6,000, and rise in cost depending on how heavy your vehicle will eventually be.

Another option is the Swindon Powertrain Classic Mini kit (pictured above), which is effectively the kit used by the British company when building its Swind E Classic converted Mini. The package comprises an HPD E Powertrain system mounted to an original classic Mini front subframe featuring brackets specifically designed for this installation. It also includes purpose-designed inner CV joint housings that allow the fitting of standard Mini driveshaft assemblies and comes with a standard differential (an optional limited-slip differential available).

This can be used in isolation or in addition to a range of aftermarket Swindon Powertrain components such as a 12kWh battery pack, motor controller, on-board charger and DC-DC converter. Swindon describes it as being "suitable for classic-car enthusiasts, specialists or conversion businesses that want to electrify a classic Mini", and you’ll need the best part of £10,000 to get hold of everything you need.

Do I need to fill out some paperwork?

Yes! The DVLA has a long and convoluted process for registering ‘radically altered vehicles’, which you must complete before your converted electric car is allowed on a public road.

First, you must follow the DVLA’s instructions for registering a new vehicle, providing a ‘built-up vehicle inspection report’ (known as a V627/1 form), evidence of type approval if needed, the original vehicle’s registration certificate, receipts for any parts used in the conversion, plus photographs of the vehicle.

A points system is used to determine what registration number your car will receive. You must qualify for at least eight of them on the DVLA’s parts list in order to keep the original registration number, and five of these must be awarded for having an unmodified chassis, monocoque or frame. Further points are awarded for having the original suspension at the front and back (two points), axles (two points), transmission (axles), steering assembly (two points) and engine (one point).

If you fail to meet these criteria – or if you’ve welded two vehicles together as part of your conversion – you must gain type approval in order to earn a registration number prefixed with a ‘Q’. For this, you’ll need to go through the Individual Vehicle Approval (IVA) scheme, which involves having your vehicle inspected thoroughly at a DVSA-approved provider of ‘designated technical services’. You’ll also need to provide documents as evidence.

On top of all that, you’ll need to get a model report costing hundreds of pounds, and ensure that you fill in the correct application form. In short, an electric-car conversion is a tall order if you’re not already familiar with UK regulations and procedures.

Can someone convert an electric car for me?

In theory, yes. There are a number of companies that offer electric-car conversions, although these tend to be focused on classic and high-performance cars. The trend for electrified classics in particular has taken off in recent years.

The reason for this is that the process tends to be very expensive. Take the DB6 MkII Volante conversion that Aston Martin is in the process of developing: the price of converting its 4.0-litre, six-cylinder petrol powertrain to an all-electric one looks set to be in the region of £200,000.

RBW is smaller British firm that's also in on the action, with plans to build a run of 30 electrified MGBs, each built using all-new parts and with a 94bhp electric motor; prices start at £108,000. The company has developed its own platform that can be licensed by other firms to make their own conversions. 

Then there’s the original MINI conversion being offered by the engineering company Swindon Powertrain mentioned above: that’ll cost you a still-very-hefty £79,000. For that money, you could get a brand-new Tesla Model S Long Range and save yourself the hassle. If you’ve got your heart set on an electric car, this is the path we’d recommend.

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