Converting an ICE car to electric is a worthy challenge.

Do you just want an EV, or do you want a project? 

We certainly don't want to discourage you, but converting a former ICE vehicle to electric is not for the faint of heart.  Mechanical and electrical work requires that the vehicle be built to a high standard.  Many parts will be custom-made and might take several iterations to get right.  Trying to fit electric components in a vehicle made for an in-line 4 cylinder engine means compromises will be made. 

Given that the used EV market is starting to take shape and new EV options are very compelling, converting a car or motorcycle to electric drive is perhaps best left for special vehicles.  Classics for which spare parts are impossible to source, or perhaps a utility or van, since most manufacturers don't yet have these options.  Maybe you happen to have a racecar project in mind?  These are good places to start, because from a financial perspective they don't make a lot of sense.  Do it because you love the challenge, or because you're preserving something special.

Francess' 1988 Honda Prelude during conversion

Many converters mount the electric motor to the manual gearbox using a precision machined adaptor plate.

What to look for in a good chassis

As a starting point, look for a vehicle with minimal rust, strong, reliable brakes and true steering.  Unless of course you are restoring a 'barn find' where rust is a fact of life, starting from a tidy chassis will save you time and money in the long run.  The chassis will ideally be lightweight, but with plenty of room for batteries and other electric components.  Battery packs will add significant weight to a vehicle's tare, so you might need to upgrade the suspension as well.  Avoid cutting into the chassis as much as possible, and where it is unavoidable, keep away from folds and seams as these provide the bulk of the torsional rigidity of the car.  When converting a motorcycle, remember that you will never have enough space for all the batteries you want. Use volume as your metric instead of weight; because if it won't fit, it doesn't matter how heavy it is.

Jeremy's electric dirtbike

Sometimes the EV you want isn't on the market yet - like Jeremy's electric dirt bike.

Choose your performance goals early

Generally a converted vehicle should have more redeeming features than the original ICE drivetrain.  More power, more torque, smoother ride - these all desirable traits.  Electric motors come in all shapes and sizes and are capable of impressive power.  But there are three things you need to know before selecting a motor: peak torque/power, continuous torque/power, and weight.  Peak numbers are deceiving.  Most motors are rated according to their constant duty; that is, how much power can it deliver all day, every day, without melting.  Peak ratings may be twice or even three times as high, but the time between smiles and molten metal will be three times shorter!  Aim for a peak power rating similar to that of the original petrol engine and tweak it from there.  You may find that the original ICE motor didn't have much torque, but was capable of revving out to 10,000 rpm.  Electrifying this vehicle may require changing the ratio of the differential, or drive sprockets in the case of a motorcycle.  Finally the weight of the motor and speed controller is important because they quickly eat up a large chunk of your mass budget.  A 60 kW industrial motor might tip the scales at over 125 kg!

Generally speaking, a brushed DC motor and speed controller will be cheaper than an AC motor and inverter, but it won't spin as fast and won't be as efficient.  DC motors usually run at lower voltages than AC motors, typically having an upper limit of 150-200 V.  AC motors usually call for higher battery voltages (300-800 V DC) and with this comes greater need for safe isolation and insulation, as well as appropriately rated components.  Most production EVs use 360-380 V as the nominal operating voltage.

Range is always a compromise - more range means more weight, and of course more money.  You will mainly be limited by what can physically fit inside the car without overloading it, or requiring the removal of rear passenger seats.  A common metric in the DIY EV community is "100 at 100" - a range of 100 km, when travelling at 100 km/h is considered very practical.  If you only plan on commuting fairly short trips, save time and lots of money by opting for a smaller battery pack.  Remember, the cheapest kWh is the one you don't need.

Daniel Booth's electric Mirage

Batteries take up lots of space so try to maximize capacity and minimize weight and volume as best you can.

Order the battery last

Only once your drive components are installed will you know how much space remains for batteries.  It certainly is possible to split the battery into two or even three separate compartments - some in the spare wheel well, some where the fuel tank was and some under the bonnet.  Remember that this means more cable, more waterproof junctions and more places for things to go wrong, so if possible stick with a single battery pack.

The voltage and capacity of the battery will be determined by your drivetrain and the space available.  Shop around for battery modules or cells which might suit your application.  Used production EV battery packs can be sourced from wreckers, but do check them thoroughly first.  

Another reason to put off the battery till last is because battery cells have a calendar life.  You might as well start with the freshest battery you can muster.  It also means you can consider thermal management of the battery pack - keeping it cool in the heat of summer wil make it last longer.

Battery packs are not cheap and might represent over half the cost of the conversion project.  Expect to pay around AUD$500/kWh for garden-variety lithium ion batteries, and over $1000/kWh for high performance cells.  Don't bother with sealed lead batteries unless you happen to have them already, and even then, test your setup using these cells before ordering some lithium.  Lead has no place in a road-going EV anymore.

Lodge your intentions with your state department of transport

Most states and territories have a specific section within the Department of Transport who specialise in modifying vehicles.  Typically you will fill out a form outlining what you intend on doing and which components you will use.  Once submitted you will be issued a notice to proceed with the conversion.  The Commonwealth Department of Infrastructure has a list of Vehicle Standards Bulletins which are relevant to the Australian vehcile fleet, with over a dozen National Codes of Practice for specific aspects of vehcile function and safety.  The AEVA was instrumental in formulating NCOP14 - Guidlines for Electric Drive.  This code which sets out minimum expectations and standards of work to be done, and is the standard to which your conversion will be assessed on by the certifying engineer.  The department will typically have a list of qualified engineers who can do these assessments, and they are typically available for consultation along the way.

Start work!

Now the fun begins!  Before getting too carried away, weigh the vehicle and try to get an indication of the front-rear weight balance.  You will invaribly change this balance, so it's good to know where it started from.  If possible, weigh each component as it is removed so you are conscious of your weight budget when adding electric components later on.  If cutting engine wiring off, try to label it so you have some idea of what buttons or gauges are attached to it on the inside of the cabin.  As a general rule, only remove wiring you know you won't need; wiring looms have a habit of being connected to far more than you think!

Mounting the drive train

There are several ways of mounting an electric motor in a vehicle - the most common is to build an adaptor plate which mates the electric motor to the gearbox.  The clutch may be kept, or if a couping can be made accurately it can be omitted.  Generally cars which retain the clutch are a bit nicer to drive, but the clutch won't get used much.  Alternatively, the entire gearbox can be removed and the motor may be mounted directly to the driveshaft.  This is more common with rear-wheel drive cars, however the differential ratio might need to be changed to suit the torque and speed limitations of the electric motor.

Another popular route is to take a complete drivetrain from a production electric car like a Nissan Leaf or Tesla, and mounting that in the chassis.  This requires very careful machining and fitment, particularly if fitting new driveshafts and suspension components.  It might not be compatible without lots of modification, so consult with your certifying engineer before going too far down this path.

Electrical safety

Electric vehicle battery packs operate at hazardous, and potentially lethal voltages.  Not only this, they are such low impedance batteries there is a serious risk of arc flash and burns.  So care and consideration should be given to cable routing and connectors, as well as future service; again, follow the advice contained in NCOP14 as a minimum.  

Fuses and contactors are essential, and consideration should be given to the pre-charge process.  Motor speed controllers have large capacitors on their DC input, and powering these without a pre-charge resistor in series will result in massive inrush currents capable of welding switch gear and damaging components.  Also consider any coolant which might be used to remove heat from the motor, controller and battery charger.  Keep all plumbing neat and tidy and restrain it so it can't rub on moving parts.

Battery management systems (BMS)

Lithium ion batteries are wonderful, but with great power comes great responsibility.  A string of cells in series will charge and discharge at the same current, but the voltage of individual cells in that string may differ.  As Li-ion cells have a maximum and a minimum operating voltage, as well as temperature limits, exceeding these limits by either over-charging, or over-discharging the battery will cause irreversible damage, and potentially start a fire.  The key to ensuring all cells are within their safe limits is the BMS.  

A good BMS will warn the driver if a cell is out of spec, and shut down the system to prevent further damage.  It will also balance the cells in series so that when fully charged, each cell contains the same amount of stored energy.  Scores of BMS options are on the market, including three made right here in Australia by members of the AEVA.  They also come with digital feedback, so you can see what each cell is up to in real time.


A good BMS gives lots of information on temperature, cell balance and stage of charge. This BMS is from ZEVA.

The battery pack should fit in the remaining space.  The vacancy left where fuel tank was is a great place to put battery packs, as this has a low centre of gravity and is protected from the rest of the chassis.  While you can put battery modules inside the cabin, it's generally discouraged as the cabin will get very hot when parked in the sun.  Ideally you can mount the main traction fuse at the half-way point in the battery, but also make sure it's reasonably accessible without too much difficulty.  This also serves as a great place to put a service disconnect in the traction circuit.


Sometimes chargers can be an afterthought, but they are the hardest working component in an EV.  So select a high quality one which is robust enough to be bolted in a moving vehicle.  Many on-board chargers are water cooled, so they can be part of the motor-controller cooling loop.  If the charger is capable of charging at up to 7 kW, it will need 32 amp AC cabling and connectors.  Make sure the charger is set to the correct DC voltage and current.  Some chargers may be changed with a specific communication system, but many are fixed form the factory.  Ensure it can be shut down by the BMS should a cell exceed its upper limit.

Type-2 charge inlet

Even conversions can get a Type-2 AC charge inlet.  This inlet is rated to 240 V AC and 32 A. 


Finally, after months (or years!) of work, you are ready to drive off down the street on its maiden voyage!  Before setting off, please check the following things - brakes.  Make sure the brakes have vacuum assistance if fitted.  Make sure all components are bolted down tightly, and all battery modules are secured.  100 kg of unsecured weight can be lethal in a hard braking situation!  Make sure the battery is charged and the BMS is working.  

Don't drive 10 km away.  Drive 1 km around the block ten times.  That way if something breaks, it's only a short walk home. Keep an ear out for any unusual sounds or indications something is not quite right.  You will become quite attuned to new noises, especially now that your vehicle is far quieter than before!


Once the vehcile is working reliably, you can call your certifying engineer to begin their assessment.  They will want very detailed wiring diagrams, photos of the build process as well as the new weights and weight balance.  Build logs on the AEVA forum are perfect for documenting the history of your project, and providing a timeline of changes for the engineer.  They will check to see that all safety systems are fully operational and that the vehcile can stop in a prescribed distance.  Only after this detailed report has been submitted to the Department of Transport for review and approved, will you be allowed to insure the vehicle as an EV.  Driving it around in an uncertified state is risky, as it won't be covered by insurance even if it's still registered.

If you want more specific advice on converting vehicles and the certification process, check out the AEVA forums or other overseas sites for informatin and inspiration.  And of course join the AEVA - we live and breath this stuff, and can't wait to help you with your conversion project!