House Power BMS reverse engineering and repair

[mbartosch]

The House Power Battery Management System was produced and sold a few years ago by CleanPowerAuto LLC which no longer exists. There was some discussion on this forum when the company closed and the sole developer of the House Power BMS joined another company, no longer providing support or spare parts for the House Power BMS.

Some cruisers still use this BMS, including yours truly. Entropy has a total of three Mini BMS (one for the house bank, two for the portable dinghy batteries which I also consider as backup for the house bank.

My three BMS and the cell modules still work, but if disaster strikes I'd like to have a backup plan (short of ripping everything apart and replacing it with a different BMS).

A few days ago I was addressed by a reader of our Blog who inadvertedly destroyed two of his cell modules. I agreed to have a look at the defective modules and try a repair. If I was successful the knowledge gained would help me if I was affected by a similar problem in the future - all while helping a fellow sailor.

I have fixed most of the problems with the two defective cell modules and, doing so, reverse engineered the schematics of the cell modules (however not yet the "master board" which controls the relays). No surprises here.

The remaining defective part is the micro controller, an ATTiny 45V. I have tried to extract the firmware of one working cell module but (of course...) the manufacturer has cleared the lock bits of the AVR, thereby preventing reading the flash memory which would allow to clone the MCU.

Now for my question: I have a pretty good understanding what is going on with the board and it would be not very difficult to write new firmware that emulates the behavior of the cell boards.

I am actually inclined to do so as a fun exercise, but before I start the work on this I would like to ask if I am missing an already existing effort to do that (don't want to reinvent the wheel here).

[mbartosch]

I analyzed the modules and built a replacement firmware. The latter tests fine in my test environment but is yet to be tested with the real BMS environment. I do not expect suprises.

Cell module reverse engineering is documented on our blog, the entire project including schematics and firmware source code is available on Github.

[markcouz]

Thanks for the effort and for making it available to all.