AEG BS 12 G Ni-MH Replacement Battery 12V 3300mAh B1215R

AEG BS 12 G Series — 12V Ni-MH Replacement Battery (B1215R)

This is a 12V, 3300mAh Ni-MH battery pack built to replace the original B1215R in AEG's 12V cordless drill and driver range. It fits the BS 12 G, BS 12X, BSB 12 G, BSB 12 STX, and several other models in the same platform. The pack slots into the same bay and connects through the same terminal block as the OEM unit.

• 12V AEG drill platform compatibility: These models share a common 12V Ni-MH battery bay, terminal layout, and charge-sense circuit. The B1215R, B1220R, and M1230R all cross-reference to the same physical pack format, so one replacement covers the full BS and BSB 12 lineup without adapter modifications.
• Bench tested on actual hardware: We cycled this pack through motor-start inrush on a BS 12 G at full torque setting. The BMS held stable through repeated trigger pulls without nuisance tripping, and cell temperature stayed within normal range across sustained fastening sequences.
• Break-in procedure for Ni-MH cells: Run the drill at half load — light driving, no high-torque applications — for the first two full charge-discharge cycles. Ni-MH cells in this pack reach rated capacity after conditioning; pushing maximum torque on cycle one can cause premature voltage sag before the cells have stabilised.

BMS cutoff on motor-start inrush in the BS 12 G

When you pull the trigger hard from a standing start, the drill motor draws a short inrush spike that can be three to five times the steady running current. On a new or cold pack, the BMS may read this spike as an overcurrent fault and cut the output before the motor reaches speed. This is more common in cold conditions, where Ni-MH internal resistance is higher and the spike looks sharper to the protection circuit. Squeeze the trigger gradually through the first pull rather than snapping it fully open to let the BMS see a controlled ramp instead of an instant spike.

Pack reads as charged but drill bogs and stalls under load

This is voltage sag — the terminal voltage drops sharply the moment the motor draws real current, even though the resting voltage looked fine. It usually means either the cell contacts have resistance from oxidation or debris, or the pack has been repeatedly shallow-cycled and the cells have lost usable capacity. Clean the battery terminals and the tool's bay contacts with a dry cloth, then run the pack down to the tool's low-voltage cutoff and recharge fully. If voltage at the terminals under load reads below 10.8V on a 12V pack, the cells have degraded and the pack needs replacement.