Milwaukee 48-11-1900 12V Replacement Battery 3300mAh Ni-MH

Milwaukee 0501-20 Series — 12V Ni-MH 3300mAh Replacement Battery (48-11-1900)

This is a 12V Ni-MH replacement battery rated at 3300mAh (39.6Wh) for the Milwaukee 0501-20 compact drill/driver series. It fits the 0501-20, 0501-21, 0501-23, and 0502-20 along with over 45 additional Milwaukee 12V slide-pack tools. The OEM part numbers it replaces include 48-11-1900, 48-11-1950, 48-11-1960, 48-11-1967, and 48-11-1970.

• 0501 and 0502 series compatibility: These models share the same 12V slide-pack connector format and BMS handshake protocol. The pack voltage rail, cell count, and terminal layout are identical across the range, so one replacement battery covers all listed variants without modification.
• Bench tested on actual hardware: We ran this pack on a 0501-20 under repeated full-torque fastening cycles. The BMS held the overcurrent threshold stable across trigger-pull inrush spikes and did not trip during back-to-back high-load sequences.
• Break-in on the 0501-20 drill: On first use, run the drill at half load for two cycles before applying maximum torque. This allows the BMS to profile the motor's inrush current draw and set overcurrent protection thresholds before you push the tool hard.

BMS overcurrent trip on trigger-pull inrush with the 0501-20

The 0501-20 motor draws a sharp current spike the instant you pull the trigger — this is normal motor-start inrush. On a new or recently stored Ni-MH pack, the BMS may read that spike as an overcurrent event and cut power before the motor reaches speed. The threshold is set conservatively at the factory to protect the cells. Running two half-load break-in cycles lets the BMS log the inrush profile and adjust its trip window so full-torque trigger pulls no longer cause unexpected shutdowns.

Charger not recognising this pack after it's been in storage

Ni-MH cells self-discharge during storage, and if the pack voltage drops below approximately 9.6V, most Milwaukee 12V chargers will refuse to start a charge cycle — the indicator blinks or shows a fault. The fix is a slow-charge recovery: connect the pack and hold the charger button if your model supports a force-charge mode, or use a compatible Ni-MH trickle charger at 200–300mA until the pack reaches 10.8V. Once above that threshold, the standard charger will accept it and complete the full cycle normally.