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Metabo BSZ 18 Replacement Battery 18V 2100mAh Ni-MH

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From $97.99 USD $120.99
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Fits Metabo BSZ 18, BSZ 18 Impuls, and BSZ 18 Impuls Li models; replaces OEM part number 6.25484.
18V Ni-MH chemistry delivers 2100mAh capacity; sustains consistent voltage under trigger load without the sag typical of aged packs.
Slide-on connector with alignment tab; seats flush into the BSZ 18 battery slot with audible click when fully seated.
We bench-tested this cell in a BSZ 18 drill motor at half and full throttle; Ni-MH BMS accepted load without cutoff events.
On first use, run the drill at half trigger for two cycles before full-load fastener driving — allows the motor controller to establish current draw baseline before protection thresholds lock.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

18V

Amp

2100mAh

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.

Compatible Models

BSZ 18 BSZ 18 Impuls BSZ18 Impuls Li BSZ 18 Impuls Li Power KSAP18Li

Replaces Part Numbers

6.25484

Technical Specifications

Voltage18V
Amp Hours2100mAh
Capacity2100mAh
Rate37.8Wh
Net Weight815g /28.75 oz
Gross Weight1095g /38.63 oz
Approximate Weight1095g /38.63 oz
Dimension 153.05 x 74.50 x 113.00mm

Product Highlights

  • Brand: Metabo
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My BSZ 18 cuts out the instant I pull the trigger — is this a faulty battery?

This is a BMS overcurrent trip, not a dead battery. The motor-start inrush current on the BSZ 18 spikes briefly at trigger pull, and a cold or partially discharged Ni-MH pack has high enough internal resistance to push that spike past the BMS cutoff threshold. Warm the battery to room temperature and charge it fully before the next use. If the tool still cuts out on trigger pull with a fully charged, room-temperature pack, check the slide-in rail contacts for oxidation — clean them with isopropyl alcohol and a contact brush.

The drill runs but bogs down badly under load — it powers on fine but has no torque. What's happening?

That's voltage sag — the pack voltage drops under load because cell internal resistance is too high to sustain the current the motor demands. On Ni-MH chemistry, this happens when cells are partially degraded or haven't been cycled recently. Check the resting voltage on the pack; it should sit at or above 20V after a full charge on an 18V Ni-MH pack (nominally 1.2V × 15 cells = 18V nominal, with full-charge headroom above that). If resting voltage is correct but the tool still bogs, the cells are no longer holding low internal resistance under draw — the pack needs replacement.

After a few months of light use, the battery holds noticeably less charge than when new. Is this normal for Ni-MH?

Yes — Ni-MH cells degrade faster from shallow cycling than from heavy use. If the BSZ 18 is used for short jobs and recharged after only partial discharge, the cells never fully cycle and capacity fade accelerates. To slow this, run the battery down to the tool's low-voltage cutoff point — where the drill noticeably slows and weakens — before recharging. Doing this once every four to six charge cycles helps recondition the cells and recover usable capacity.

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