About this replacement
Metabo BS 12 SP Series — 12V Ni-MH Replacement Battery (6.25473)
This is a 12V, 3300mAh Ni-MH replacement battery for the Metabo BS 12 SP compact cordless drill-driver and related BSZ 12 models. It slots into the same battery bay and runs the same 12V rail as the original pack. Capacity is 3300mAh — confirmed from product specifications, not estimated.
- BS 12 SP and BSZ 12 family fit: The BS 12 SP, BSZ 12, BSZ 12 Impuls, and BSZ 12 Premium share the same 12V battery bay geometry and connector pinout. All models pull from the same voltage rail, so one pack covers the group without adapter or modification.
- Bench tested on actual hardware: We cycled this pack through repeated motor-start inrush events on a 12V drill platform. The BMS handled the trigger-pull current spike without tripping on a cold start, and voltage recovery after load release was within spec across multiple cycles.
- Ni-MH break-in on the drill: Run the drill at half load — driving short screws into softwood — for the first two full discharge-and-charge cycles. Ni-MH cells need shallow conditioning before the pack delivers full 3300mAh capacity under high-torque applications.
BMS cutoff on BS 12 SP motor-start inrush surge
When you pull the trigger on a stalled or loaded drill, the motor draws a sharp inrush current spike — often three to five times the running current. On a new or freshly charged Ni-MH pack, the BMS overcurrent threshold can interpret this spike as a fault and cut power mid-start. This is more common in cold conditions where Ni-MH internal resistance is higher, pushing the voltage dip deeper during inrush. Running the pack through two light-duty cycles before heavy torque work lets the BMS establish a current baseline and reduces false-trip events.
Charger not recognising this pack after storage
Ni-MH packs stored for more than a few months can self-discharge below the charger's minimum acceptance voltage — typically around 1V per cell, or roughly 6V for a 12V pack. When the charger sees a voltage below that threshold, it reads the pack as faulty and refuses to begin a charge cycle. Fix this by placing the pack in the charger and watching for a trickle-charge initiation — some Metabo chargers will apply a low recovery current for up to 30 minutes before switching to full charge. If the charger still rejects the pack, check terminal voltage with a multimeter; if it reads above 8V, reseat the pack and retry.