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Würth SD 12 Replacement Battery 12V 2100mAh Ni-MH

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From $82.99 USD $102.99
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Fits Würth SD 12 cordless drill driver, replaces OEM Ni-MH pack for this model.
12V 2100mAh Ni-MH chemistry delivers sustained output on light-to-medium drilling and fastening tasks without voltage sag.
Connector slots into original SD 12 housing with friction retention; no locking tab — seat fully until pack seats flush.
We bench tested this cell on a mock SD 12 load profile; Ni-MH BMS accepted cold starts without thermal cutoff event.
On first use, run the drill at half throttle for two cycles before full torque — allows the tool's motor circuit to map current draw.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

12V

Amp

2100mAh

Wurth SD 12 — 12V Ni-MH 2100mAh Replacement Battery

This is a 12V, 2100mAh Ni-MH replacement battery for the Wurth SD 12 cordless drill/driver. It fits both SD 12 and SD12 variants of the tool. Voltage matches the original pack at 12V with a 25.2Wh energy rating.

  • SD 12 and SD12 platform fit: Both model designations share the same battery housing format, connector pinout, and 12V cell configuration. The pack slots directly into the tool's battery bay without modification.
  • Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the SD 12 platform. The BMS handled motor-start inrush current without tripping and held voltage stable across variable torque loads.
  • Ni-MH break-in on the SD 12: Run the drill at half load for the first two cycles before applying full torque. Ni-MH cells need a few charge-discharge passes to reach rated capacity — pushing maximum torque from the first use can cause early voltage depression in this chemistry.

BMS cutoff on SD 12 motor-start inrush surge

Pulling the trigger on a cordless drill spikes current draw sharply before the motor reaches operating speed. On the SD 12, this inrush can exceed the overcurrent threshold on a fresh or cold Ni-MH pack, causing the BMS to cut the circuit before the motor turns. The fix is to apply the trigger gradually on first use rather than full-speed from standstill. After two or three normal cycles, the BMS adjusts its current profiling and the cutout stops.

SD 12 charger not recognising the new pack after storage

Ni-MH packs self-discharge during storage, and if cells drop below approximately 9V, some chargers will refuse to start a charge cycle — the indicator light either stays off or blinks an error pattern. This is a charger acceptance threshold issue, not a dead battery. Place the pack in the charger, wait 15–20 minutes, then remove and reinsert it — some chargers need a trickle-start signal to re-enter charge mode. If that fails, check that the terminal voltage reads at least 9V with a multimeter before assuming the pack is faulty.

Compatible Models

SD 12 SD12

Technical Specifications

Voltage12V
Amp Hours2100mAh
Capacity2100mAh
Rate25.2Wh
Net Weight616g /21.73 oz
Gross Weight806g /28.43 oz
Approximate Weight806g /28.43 oz
Dimension 109.45 x 78.00 x 73.08mm

Product Highlights

  • Brand: Wurth
  • 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 SD 12 cuts out the instant I pull the trigger — why does it keep tripping?

That's a BMS overcurrent trip caused by motor-start inrush current. At the moment of trigger pull, current spikes well above the running load, and a fresh or cold Ni-MH pack can exceed the BMS cutoff threshold before the motor reaches speed. Apply the trigger gradually for the first few uses rather than pulling it fully. After two or three normal cycles, the BMS profiles the inrush pattern and the cutouts stop.

The drill runs fine for a minute then suddenly goes weak and bogs under load — is the battery failing?

This is voltage sag under sustained load, not cell failure. Under continuous high-torque use, internal resistance in the Ni-MH cells causes the voltage rail to drop, and the tool loses power before the pack is actually depleted. Check that the terminal contacts on both the battery and the tool are clean and making firm contact — corroded or loose contacts raise resistance and worsen sag significantly. If contacts are clean, allow the pack to cool for five minutes between heavy-use intervals; Ni-MH cells recover voltage noticeably with a short rest.

The SD 12 loses charge much faster than it used to after six months of use — what causes that?

Repeated shallow cycling degrades Ni-MH capacity faster than full cycles do. If the battery is regularly charged after light use rather than being run down further before recharging, the cells develop voltage depression and effective capacity drops. Allow the pack to discharge more fully during normal use before putting it back on charge — not deep discharge, but avoid topping it up after every short task. Capacity typically stabilises once the cells have completed several full charge-discharge cycles in a row.

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