What is " charge recovery voltage" on BMS

I seem to be ending up with a stack of cheapo 2S2P light packs that all have the same vault, they won't charge. They seem to be able to discharge down to normal levels where the BMS cuts in Ok. Everything else seems OK and I can charge directly to the battery by bypassing the BMS.

Now in the BMS data sheet it mentions charge recovery voltage. Is the charger over volting the battery, the BMS cuts in, we then discharge the battery and then the BMS is unable to reset that charging over voltage trip out ? If that is the case do we need to bring the battery back up to in this case 4.075V per group of cells or am I miss reading this.

Thanks

That's the voltage it'll bring the high cells down to before it starts charging again. So basically it will charge until a cell hits 4.275V, then it will bleed off the high cells until they are all below 4.075V. Then it starts the process again, until all the cells are balanced.

Eventually you will hit the termination voltage of your charger, with balanced cells. At that point they should all be very close to 4.2V.

That model apparently does not have balancing, so the recovery voltage is what the cell would need to be drained to before charging would start again after it triggered an overvoltage shutdown but it would need to be drained externally.

fechter said:

That model apparently does not have balancing, so the recovery voltage is what the cell would need to be drained to before charging would start again after it triggered an overvoltage shutdown but it would need to be drained externally.

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Damn, you're right.

Thanks guys,

Don't think there is any balancing going on, seems a bit strange that it simply won't charge the cells, I guess there's some sort of common failure on the charging side of the board.

You could manually charge the 2 cells individually to the same voltage and see if will work normally then. Since there's no bleed circuit involved (because there's no balancing), inability to stay in balance probably indicates a bad cell (versus a stuck on bleed resistor)

They are quite new cells of good quality so blaming the board more than the cells. I'll recharge them up to mid voltage manually and then recheck in the morning to see if there is a big imbalance.

Thanks.

As long as none of the cells are over 4v, it should charge. Another thing to try is disconnecting the BMS and reconnecting it, which should reset the monitors. Once reset, it should charge as long as none of the cells are over 4.275v.