How To Convert Your Car Into An EV

Engine swaps are common in the car modification scene, but divulging completely from internal combustion is a much rarer and unspoken craft. With the majority of current manufacturers moving towards electric powertrains through hybrids and full-on EVs, hobbyists have also been turning their attention to the electric motor. It may seem sacrilegious to the most-staunch of petrolheads but converting an old banger to an EV does have its merits and may be a great way to cushion the blow of incoming electric domination. So here’s a basic guide of how to go about it.

Pick a suitable car

Simplicity is key here; anything that once worked off engine power is useless to you. Power steering and assisted braking are no good, we need complete analogue controls for this purpose. Excess weight is no good either as this will only apply unnecessary load to the batteries and electric motors. So no electric windows, heated seats or luxuries whatsoever.

Something like a Chevrolet Sprint or Honda Civic would be ideal, and of course you can go for something ultra-cheap because the engine can be a non-runner. This exposes an area of the secondhand market that you probably don’t bother delving into and many options can be found for under £500.

Pick an electric motor

There aren’t too many options that will be cheap and reliable for the task at hand. Forklift truck motors are a popular choice, using 12-72V DC motors that spin at around 3500rpm. The size of the motor depends on the size/weight of the vehicle, so a car like the Chevy would only need a small electric motor to produce decent performance. You can fetch a solid 72V motor for around £200 secondhand, either from a forklift truck or milkfloat.

Strip the car of all internal combustion components

It’s now time to strip out the entire powertrain. Out comes the engine, radiator, fuel tank, starter motor, exhaust system and fuel lines. Without compromising any safety gear, other components can also be stripped for weight saving like fluid reservoirs and the distributer.

Make sure to drain the fuel tank properly before removal and be clever with the parts you’ve just removed; if the car only cost £500, you can probably make a profit through simply selling these now unwanted components.

The electricity has to connect to the wheels somehow, so the original transmission of the car is retained. An adapter plate needs to be machined out of a billet of aluminium and then further machined to incorporate the necessary mounting holes to connect the electric motor to the transmission. A template will need to be drawn out first to situate all the mountings where they need to be, along with making sure that the input shaft of the transmission and the output shaft of the electric motor will line up perfectly.

A bit of welding is then needed to link the two shafts together. A toothed adapter needs to be welded to each shaft, meaning the electric motor and transmission can be mechanically linked to transfer power to the wheels. These will need splines machined through them to mesh with each shaft before coming together with a mechanical coupling to form the connection.

Batteries and controller

The amount and size of the batteries needed depends on which motor you’ve picked - for example a 72V motor will need six 12V batteries. Considering lead acid batteries can weigh in at around 12kg each, weight distribution comes to the forefront. It’s recommended to put two thirds of the batteries in the boot, with the rest under the bonnet to offset the placement of the powertrain. Link the batteries up to one power inlet and a simple plug can be put in the place of the petrol filler for overnight charging.

A controller is needed to regulate the power from the batteries to the electric motor, and these are rated using current values (in amps) and then relating to a voltage range. The controller uses a potentiometer to provide an electric ‘throttle’, allowing regulation of the battery power. This is then connected to the throttle pedal to provide an electrical signal between the two.

Rebuild the car

Using an engine hoist, position the new powertrain back into the car and reconnect the rest of the drivetrain to the new system. Connect up the batteries, and you’re ready to go!

Depending on the size of the electric motor and amperage of the controller, you can expect a range of around 20 miles when driving at normal town speeds with this kind of setup. Considering the motor is engineered to shift a forklift weighing four tonnes, acceleration will always be fairly impressive considering how light the vehicle will now be in comparison, but top speed will be limited to around 70mph at a push as the electric motor can’t spin any faster.

Problems arise with the costs that come with replacing batteries every two to five years, charging times of up to eight hours, increased suspension travel due to a decrease in weight over the front axle and the rate that the batteries drain. Although an EV of this kind would be capable of 70mph, the power supply would drain extremely quickly, limiting the car to slow town driving.

Mechanical issues are common as well, especially at the coupling between the electric motor and transmission. If alignment is slightly off, the vibration and wobble of the shafts can lead to failure and a rebuild of the connection will be required. Despite these issues, converting an old hatchback to an EV would be an interesting project for those willing to put in the time. It would provide an insight into the way in which the automotive industry is leaning but from the sanctuary of a once IC-powered chassis.

Could this be your next project car? Does this form of ‘restoration’ appeal to you? Comment with your thoughts below!