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Reverse Engineering the A123 BMS
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x and I started working on reverse engineering the Battery Management System board that comes on the A123 packs. It seems to be based around a PIC microcontroller, with a bunch of voltage dividers to read the cell voltages, shunt resistors and MOSFETs to balance the cells, and an serial port isolator to allow it to communicate with the next battery pack up, allowing the BMS boards to be daisy chained via the 5 pin connector.

Current list of identified chips:
Microchip dsPIC30F5011 TQFP-64 microcontroller
ADUM2401 Quad-Channel Digital Isolator
ISL21009BFB841Z 4.096V Voltage Reference
Crystal marked ECSR7.3EX, unknown
24LC1025 EEPROM
LM2937 5V LDO Regulator
LT3437 Switching Regulator

In order to use this as a BMS, we need to figure out the pinout for the connectors, then either figure out all the serial commands they use to control it, or write our own firmware for the PIC. I contacted the project lead for this BMS, we'll see if he can share any details on the protocol, but I wouldn't bet on it.

As this board is too big to fit in any of my projects for these cells, I'm mostly interested in it for testing the cells. But I think a lot of DIY Powerwall people would like to use this board for it's intended application.
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