My take on Collin's BMS. Changes listed below:

• Now balances to the lowest cell between two packs connected together in series.
• CSV output for those that might use it.
• Cells balance for 30s and then update again, turning the balancers off momentarily to get accurate readings.
• Baud set 612500 (I have older Tesla packs)

See it in action here: LongDog Power Plant

Arduino compatible project to interface with the BMS slave board on Tesla Model S modules.

The modules are daisy-chained together with a TTL interface. The interface uses a Molex 15-97-5101 connector and runs at 612500 baud. This can be a difficult baud rate to match with arduino compatible processors. The Arduino Due and Teensy 3.5/3.6 boards are confirmed to be able to generate a suitably close baud rate. The factory wiring to each module is comprised of two sets of 5 differently colored wires:

• Red = 5V input to the module
• Green = Gnd for power and signal
• Gray = Fault output
• Yellow = UART Wire
• Blue = UART Wire

The fault output is active low. Use your own pull up to the fault line and if the line is pulled low then a fault has occurred.

Here is a PDF that explains how the wiring between modules and the master board is supposed to be: https://cdn.hackaday.io/files/10098432032832/wiring.pdf