OK, I built a 8 volt drop for a spoof on pin 1 and everything works well. Zivan Charger on “F” for high voltage trojan will get cells to 91 volts. Some balancing occurs near the top. Cells are balanced to within 0.012 to 0.040 volts depending on where in the cycle they are. We will see if this closes up with a few cycles but it works as is. I drove around town yesterday from 100% to 75% charge. Went as far as I will ever go in a single trip. Factory dash gauge was at 100% the whole trip but dropped to 95% as I pulled in my driveway. The car easily reaches 28 mph except on hills. Now goes 23 uphill where it used to do 19 on lead. I think that is at the limit of the motor or controller. Annoying thing that is worse now with Lithium is the pedal to the floor on any sort of downhill the controller alternates between mild acceleration and full regeneration braking in a 10 second cycle. It did this on lead batteries too. It does the control smoother if I let off the Pedal slightly, but I lose a precious mph or two. I am monitoring the batteries with the display for the BMS, but I will probably remove it after a few cycles and let the BMS do its job on its own. Then I will just use the display as a service tool every few cycles. If the Dash gauge gives me some reasonable warning of low charge I would likely not even need the BMS at all when I get further into this. but it does give peace of mind at this point. The BMS does drain the battery slightly at rest. Without the BMS and with the battery switch off the pack does not seem to discharge at all. I installed a bypass switch on my Spoof, so if the controller cuts out on low voltage I should be able to activate a reserve to get home. I have to do more driving to test this function and discover how the bottom end of the charge behaves.
22 cell 55ah Chevy Volt from INWO (one off, not a regular product)
BMS including display from INWO (one off, not a regular product)
2002 4 seater GEM car
Stock 5Hp motor (Original ?)
Stock T2 controller
Stock Zivan Charger with Trojan / Gel rebuild sticker for “C” and “F”.
Home Built 8 volt spoof on Pin 1 of 23 pin plug
I plan to add a MM speed spoof to see if the top end behavior improves on hills. If it does not help, I might get into T2 programming but that opens up a new bucket of fish.
BTW my one trip without the heavy batteries did not show a big difference in the ride quality. It still sucks. It just does not seem worse. I have all 55ah of batteries under the hood. I did keep the long battery wires in series as I kept the factory battery disconnect in the circuit. Years ago I had mounted the switch through the panel where the charge plugs in so I can switch it off with the seat in place. With the wires already there I thought a disconnect switch away from the business end of the installation might be a good safety practice.
So this is as close to stock 2002 GEM can be and still run 90 volts of lithium. I think no matter what, the additional voltage provided by 22s Lithium ion or 24s LiFePo, or 7s 12 volt lead batteries, is a worthwhile modification to these cars to make them run to at least close to the minimal promise of the original manufacturer’ sales brochure. I think the stock build met the manufacturer’s real original goal (which was to meet a quota for number of Zero emissions vehicles built).
If you read this far, here is the ironic purpose I use this car for the most. I drive to the gas station to get real gas for the boat and the lawn mower.