I want a cheap EV Conversion
Cars can be converted to electric at very reasonable cost, as long as you have the skills and realistic ambitions. Pay attention to the warning above.
With that out of the way, here’s how you might go about building a cost-effective EV conversion.
Unless you already have a car, start by getting hold of a motor and inverter and getting the motor spinning. This will give you a sense of what you are undertaking with the minimum investment, as the car and batteries will likely be your biggest costs. Work out which of the options below might best fit your planned project, and choose an appropriate control method - OI board, ZombieVerter, or one of the other options out there.
You can power this trial set up using a benchtop power supply, a few 12V lead acid batteries, or rectified mains (again, if you know what you are doing). Follow the instructions for spinning the motor using the motor in Open Loop, with the FOC firmware, or with the ZombieVerter as appropriate.
Once you're comfortable that you can build a working drivetrain, move on to choosing a car.
Choosing the Car
Rule 1: Don't buy a rust bucket.
This is the quickest route to making a cheap conversion into an expensive one. You would be spending time and resources on fixing additional parts of the car and are not able to focus time and effort on the actual conversion process. Ideally start with a reasonably maintained, working car (some funds recovered from component sale) or one that would be uneconomical to fix (big engine/gearbox overhaul required). Something with a current MOT/TUV certificate, or equivalent, would be a smart choice.
Batteries are most easily mounted in simply-shaped boxes. Consider where you might put these when choosing a car. Will you give up the boot? Is there space under the bonnet with the ICE removed? Really small cars can be challenging. Google underbody pictures of cars that you're considering, especially if variants with alternative fuels (PHEV, CNG etc.) exist.
Think about the size of battery pack you need. A relatively small hybrid pack (<10kWh) can make for a very capable city runabout. But for longer ranges you would need a larger pack or multiple packs.
How will you power the car? Is it front or rear wheel drive? Will you bolt the electric motor up to the existing gearbox? (Yes, you can have an EV with a manual box) If so you will need to make up (or have made) an adapter plate and coupler. Or will you link the motor/drive unit direct to the wheels, requiring custom drive shafts.
Older cars will have largely mechanical or individually wired systems for brakes and instruments etc. These systems will largely not care what power plant is installed and keep working. Later cars will likely use LINBUS or CANBUS. And the most recent cars might use formats like FlexRAY. In order to re-use existing systems you will need to find a way to integrate your new drivetrain with the existing systems. For some vehicles, this work has already been done and may be included in the code for the ZombieVerter. For others there might be standalone solutions, or existing knowledge on the forum/wiki. But with some vehicles, you might have to find your own answers (please share them if you do).
Your best bet for simplicity would be to use a car with electric power steering already as standard. Either EPAS or EHPAS (electric hydro pump). This will save you time and €€€ on integration.
OEM cars that have EPAS are:
- Renault Clio
- Fiat Punto, Fiat Panda
- Opel Corsa
- Audi A2
- VW Touran
OEM cars with EHPAS are:
- Opel Astra G
- Škoda Fabia
Motor and Inverter
To keep things simple (and cheap), you will want integrated components that fulfill multiple functions in your build at the same time. Proven combinations include:
- Toyota Prius Gen2 Inverter and transaxle
- Toyota Prius Gen3 Inverter and transaxle
- Nissan LEAF "stack"
- Mitsubishi Outlander Rear Drive Unit & Inverter
Batteries are likely to be your biggest cost other than the car. Perhaps the cheapest option is re-use a PHEV pack from a BMW or VW, though the market is fluctuating all the time. This will typically provide you with 8-12kWh of batteries in a small number of compact modules, interconnects to hook them up, and a 'safety box' from which you can re-use the contactors, fuse, pre-charge resistor and relay.
Alternatives would be the Nissan Leaf battery modules and BMS, though these can be more work in repurposing.
AC Charging & DC-DC Convertor
Low power chargers from the likes of the Mitsubishi Outlander are available relatively cheaply and also provide an easy-to-use DC-DC converter. Likewise the Nissan Leaf PDM gives you everything you need.
The Prius inverters can also be used to provide charging and DC-DC conversion for a truly compact option.
Smaller battery packs can be compensated for by enabling rapid charging. ChaDeMo and CCS are both now available as DIY options, using a variety of control options - notably the BMW i3 LIM for CCS.
If you are on a budget, make sure your locality allows what you are trying to do:
If you are looking for a performant ev conversion check the sister page.