Recovering a 1.9kWh li-ion battery to repurpose it.

[najrao]

 I have this 'Cube2' EV 2-wheeler battery, history unknown. It has 168 × NCR18650BD 3180mAh×30A Panasonic cells, in 14S×12P formation, and has a nominal rating of 50.4V, 38Ah. The BMS and external communication interface are out of this world, as is the whole construction and packaging.

I may have recovered the neglected battery by slow, monitored charging. I put in some 12Ah over 16 hours, starting with 500mA and ramping up to 2A over the hours. It is now at a rest voltage of 49.7, a little under 3.6V per cell. I charged with the BMS bypassed. The 12 parallel banks are remarkably well voltage-balanced, the spread being less than 40mV.

I have stopped further charging for now, and the self-leakage over 24 hours was 80mV in 50V! A short burst of fast charging at 6A incremented the voltage only 400mV, so degraded internal cell resistance  does not appear to have set in. I do have a 54.6V 6A li-ion charger, and can tweak the voltage up a little for full charge of 14S battery,  or leave it alone for extra battery life.

Now, the BMS board has no strange connections from the battery: other than the two power wires, there are just the normal inter-cell taps  to a dedicated socket, and four 6k ntc thermistors to another. However,  another socket branches out to a display and 'communications' board. This has 4+2  bicolor LED's and a bluetooth chip and much else! I don't know the much else just yet. Connections to the outside world are at a dedicated 'power' socket, which also has four 'signal' pins, detail unknown. With these latter unused, the BMS does not turn its power switches ON for charging or discharging.

The manufacturer's colorful webpages hide every technical detail meticulously, and 'download datasheet' which is offered after registration, does not work. I am not familiar with the practice of other manufacturers, and so know no more.

If only I can get the BMS to do its stuff and let me charge and discharge safely, I would put this battery to use to power a big UPS.

I do have two other 7S 40A balancing+BMS boards. Perhaps there is a way of operating them in series for the 14S needed?

Any insights and advice would be immensely helpful, thank you sirs.

Edit 1: 12//, not 14, corrected.

[thm_w]

Anything on the microSD card?
You can try to trace the four signal pins, see if they end up on a CAN transceiver or if they go to IO.

Can you add a photo of the communications board. Maybe if you figure out how to power that up, it will use some generic bluetooth app?

[najrao]

[ Specified attachment is not available ]Thank you, thm-w.

These are deep waters,  and I never learned to swim!

I attach more pictures, both sides of the two boards. And a correction: the bluetooth chip is on the back of the main BMS board, not the comm one.