The electronics work for my Toyota MR2 EV has turned out to be one of the most complex parts of the project. This work involved repairs and modifications to the original automotive electronics, and the design and implementation of new control circuits, making an electric heater out of a toaster, building the charging system, and of course wiring up the battery, motor, and controller.
As there is a lot to cover here, I've broken this section into multiple pages, that more or less cover the work in the way that I broke it up to tackle it. There are also separate pages do discuss the EV Electronic Components Overview and EV Wiring Schematics in detail.
Automotive electrical system repairs
During the process of stripping down the car (detailed on the EV Weight Change Page) I cut out a large section of the wiring harness that went through the engine bay. I also removed a lot of electronic components, such as the engine control computer (ECC) that I knew would no longer be needed. Once the carnage was finished, I had to figure out how to restore function to the remaining necessary systems of the car. This included relocating some of the circuits, and adding a DC-to-DC converter to replace the original alternator. Look at the EV Automotive Electronics page for details on my repairs to this.
Once the original EV Automotive Electronics were more or less working again, the next step was to design and implement the necessary control circuts for the car. These are new 12-volt circuits that allow me to control the speed and direction of the car and monitor the status of the car. These circuits also incorporate several safety related features including warning lights and safety interlocks. Look at the EV Control Electronics page for more details.
There is no waste heat from the engine in an electric car to power a heater with. Therefore I had to find a new way to provide cabin heat and defrost window glass during cold weather. I ended up heavily modifying a department store toaster to do this job. My EV Toaster Heater page goes into the details on this.
My Toyota MR2 EV incorporates and onboard charging system using a Russco 24-120 charger with several accessories. Using it, I can charge the car off of any 15 or 20 amp 110-volt outlet. A full charge from empty will probably take 15 to 20 hours, but a more typical charge time (based on not fully discharging the batteries, with is bad anyway) will be overnight. A significant boost would be available with only a couple hours of charging. The Russco is not the fastest, or fanciest charger available by a longshot, but it is economical and will certainly work. More details on the EV Charging System page.
Motor, Controller, and Batteries
This is the circuit with the BIG wires. It fairly simple compared to what went into getting the rest of the electronic systems going, but of course this is probably the most critical to get right. This system must be able to transmit many kilowatts of power from the batteries to controller and motor. My EV Traction Circuit is somewhat unusual for an EV Conversion in that I have a reversing contactor instead of a mechanical reverse gear. This circuit also must incorporate fuses, a circuit breaker, and a main contactor for safety and control purposes. The EV Traction Circuit page covers all the details.