I have an old (2009) GBH 36 VF-LI Bosch hammer drill but the battery has very low capacity. I would like to refurbish this battery for use with the drill. I opened the battery to find a 10S 2P arrangement, with no cell balancing wires at all, there are only two heavy gauge wires going to the positive and negative of the 10S string. The only protection/circuit in the battery appears to be a thermistor, I believe this is used to stop the charger if the battery is hot. I think the third pin on the battery communicates with the charger and provides the battery temperature healthy status.
The charger draws about 180W measured using an AC adapter. This seems a little high for a 2P arrangement. It appears to terminate charging at about 40.7V, (<4.1V per cell).
I was hoping to re-pack with some used LGEBMG 18650 cells I have on hand which I've tested to have better capacity. I have access to a spot welder, can balance the cells, and know enough to do this but am reluctant to build a pack without a cell balancing BMS for charging. Does anyone know why/how a reputable manufacturer makes batteries without cell level BMS? Is it unwise to just re-pack and hope for the best? What other solutions can you suggest?
The charger draws about 180W measured using an AC adapter. This seems a little high for a 2P arrangement. It appears to terminate charging at about 40.7V, (<4.1V per cell).
I was hoping to re-pack with some used LGEBMG 18650 cells I have on hand which I've tested to have better capacity. I have access to a spot welder, can balance the cells, and know enough to do this but am reluctant to build a pack without a cell balancing BMS for charging. Does anyone know why/how a reputable manufacturer makes batteries without cell level BMS? Is it unwise to just re-pack and hope for the best? What other solutions can you suggest?
