With the inverter apart, we decided to replace the logic system as well, using the OpenInverter system (see the Components area for more information). But after blowing a couple of $150 IGBTs due to sheer stupidity, we went for a Chevy Volt inverter (also $150) which provided an excellent system after some tuning.

The horrific Leaf batteries were replaced with 12 Chrysler/LG Chem modules from the Pacifica hybrid minivan. Each module is 60V, 45Ah, for a total capacity of 32 Kwh (I have measured up to 31Kwh used). These modules are still all mounted in the engine compartment. The construction of the battery holders and the circuitry for the power and the monitoring wires took months of careful planning and then weeks of measuring, cutting, welding, and painting. Fortunately these are excellent batteries, delivering at least their rated capacity and staying nice and cool while moving the car 75mph in 105-degree temperatures.

I decided not to repeat the insane amount of wiring which the Leaf BMS required, instead building my own distributed and customizable BMS solution. (See Components/Custom BMS).

With all this custom work, it seemed a shame to skip instrumentation. So I pulled out a Raspberry Pi and CAN adapter and began writing Python, Javascript and HTML, resulting in a simple webserver which displays realtime information from the inverter, DC/DC and BMS all on an Android tablet connected via WiFi. Update speed is 100ms with room for lower latency (sometimes very useful when tracking inverter behavior).

The car now performs very well at speed and over long distances. I have not yet attempted a long-range test, but on one trip covered 90 miles and still had some power to spare, having used 30.8 Kwh out of the nominal 32. Most trips will only be 40 to 45 miles at highway speeds, so the range is ample. Top speed is well over 110mph (tested to 97, ran out of road at that point) and the handling is wonderful. Acceleration is excellent at most speeds.

Of course it can't all work well, and so the motor does not behave well at low speeds. This is probably due to noise in the motor encoder, the sensor which informs the inverter brain of the motor's position and speed. The issue manifests itself in low-speed jitter and shaking, and occasional overcurrent events when pulling away from a stop light. These issues can be solved with some more careful measurement and debugging.

The cost of the components in the car has not increased. However, another $4000 was spent on new components (mostly batteries and BMS) and some was recouped by the sale of the old batteries for  use with solar.