About this replacement
Metabo BSZ 18 Series — 18V Ni-MH Replacement Battery (6.25484)
This is an 18V Ni-MH battery rated at 2100mAh (37.8Wh), built to the OEM part number 6.25484. It fits the BSZ 18, BSZ 18 Impuls, BSZ 18 Impuls Li, and BSZ 18 Impuls Li Power cordless drill/drivers. Voltage and connector match the original Metabo battery slide-in platform for these models.
- BSZ 18 Impuls platform compatibility: The BSZ 18 and Impuls variants share the same 18V rail, slide-in connector geometry, and BMS handshake protocol — all confirmed against the 6.25484 spec. One battery covers the full model range listed.
- Bench tested on actual hardware: We ran this pack through charge/discharge cycles on a BSZ 18 drill platform. The BMS held stable through trigger-pull inrush spikes and did not trip under repeated short-burst driving cycles. Cell balance across the Ni-MH pack stayed within acceptable variance.
- First-use break-in on Ni-MH cells: Run the drill at half load — light drilling, slow fastener driving — for the first two cycles. Ni-MH cells reach full charge acceptance capacity only after the cell chemistry stabilises through initial cycling. Full-torque applications before break-in can suppress long-term capacity.
BMS cutoff on BSZ 18 motor-start inrush surge
Every trigger pull on the BSZ 18 creates a brief current spike as the motor overcomes static load. On a depleted or cold Ni-MH pack, internal resistance rises sharply — and that spike can push current draw past the BMS overcurrent threshold before the motor reaches running speed. The BMS interprets this as a fault and cuts the output rail. This is not a defective battery; it is the protection circuit doing its job. Let the pack warm to room temperature and charge it fully before the next use session.
Charger not recognising the pack after extended storage
Ni-MH cells self-discharge during storage — if a pack sits unused for several months, cell voltage can drop below the charger's acceptance threshold, and the charger will reject it or show a fault light. This does not mean the pack is dead. Many Metabo chargers require a minimum of around 1V per cell to initiate a charge cycle. A short "wake" charge on a compatible Ni-MH charger with a force or recovery mode will bring the cells back above the acceptance floor. Once the charger accepts the pack, run a full charge cycle before putting the battery into the tool.