About this replacement
Metabo BSZ 14.4 Series — 14.4V Ni-MH Replacement Battery (6.25475)
This is a 14.4V 3300mAh Ni-MH replacement battery for the Metabo BSZ 14.4, BSZ 14.4 Impuls, SBZ 14.4 Impuls, and SBZ 14.4 Impuls series cordless drill/drivers. It matches the OEM part numbers 6.25475 and 6.25476. The pack slots directly into the original battery bay and communicates with the factory charger.
- BSZ and SBZ 14.4 platform fit: These models share the same 14.4V rail, battery connector, and BMS handshake protocol. The pack geometry and contact placement are identical across the BSZ 14.4, BSZ 14.4 Impuls, and SBZ 14.4 Impuls variants, so one battery serves the full lineup.
- Bench tested on actual hardware: We ran this pack through full charge and load cycles on a BSZ 14.4. The BMS held stable through repeated trigger pulls, and the charger accepted the pack without fault codes or termination errors.
- Break-in procedure for Ni-MH cells: On first use, run the drill at half load for two full discharge-charge cycles before applying maximum torque. Ni-MH cells need a conditioning period — skipping this leaves usable capacity unrealised and can cause premature voltage cutoff under heavy fastening loads.
BMS cutoff on motor-start inrush during hard drilling
When a drill bit bites into dense material, the motor draws a spike of current before it reaches operating speed. On a 14.4V Ni-MH pack, this inrush can exceed the BMS overcurrent threshold — especially if the cells haven't been conditioned. The BMS trips to protect the cells, and the tool cuts out instantly mid-hole. Running two break-in cycles at reduced load gives the BMS current data to calibrate its trip threshold before you push the pack hard.
Tool bogs and loses torque under sustained load
If the BSZ 14.4 feels weak or slows during long fastening runs, the issue is usually voltage sag — the pack voltage drops under load as cell impedance rises. On a used Ni-MH pack, this is often caused by cell sulfation from repeated shallow cycling. Check the rail contacts on both the battery and the tool for oxidation first — dirty contacts add resistance and worsen sag. A fully discharged and recharged pack should hold above 12.5V under moderate drilling load; below that, cell degradation is the cause.