Milwaukee 12V Ni-MH Replacement Battery 0502-23 2100mAh

Milwaukee 0502-23 / 0502-25 Series — 12V Ni-MH Replacement Battery (4 932 367 904)

This is a 12V, 2100mAh Ni-MH replacement battery for the Milwaukee 0502-23, 0502-25, and 0502-52 cordless drill/driver platforms, along with the 12V Power-Plus series and over 30 additional compatible models. It replaces OEM parts 4 932 367 904, 4 932 376 508, 4 932 373 522, 49-24-0150, and PBS 3000. Voltage, cell count, and connector geometry match the original Milwaukee pack specification.

• 0502 and 12V Power-Plus compatibility: These models share a common 12V rail, identical slide-in connector, and the same BMS handshake protocol. The cell configuration — ten 1.2V NiMH cells in series — is consistent across the 0502-23, 0502-25, and 0502-52 variants, which is why one pack covers the full range.
• Bench tested on actual hardware: We cycled this pack on a 0502-23 through repeated drill and fastening loads. The BMS held overcurrent protection thresholds correctly during trigger-pull inrush and released cleanly after each load cycle with no false cutoffs.
• Break-in procedure for NiMH packs: Run the drill at half load — light fastening or low-torque boring — for the first two full discharge cycles before applying maximum torque. This lets the BMS profile the motor's inrush draw and set accurate overcurrent thresholds before hard use.

BMS cutoff on motor-start inrush surge in the 0502 drill

When you pull the trigger on a Milwaukee 0502 drill, the motor draws a brief high-current spike before reaching operating speed. On a new or recently stored NiMH pack, this inrush can exceed the BMS overcurrent threshold if the cells haven't been cycled yet. The BMS trips, the drill cuts out instantly, and the pack feels dead — even though capacity is fine. Two half-load break-in cycles recalibrate the threshold and eliminate this behaviour.

Tool bogs under load and voltage drops noticeably mid-task

Voltage sag under sustained load — driving long screws or boring through hardwood — points to elevated contact resistance at the battery rail or early capacity fade from repeated shallow cycling. Check the slide-in connector terminals on both the pack and the drill for carbon deposits or corrosion; clean with isopropyl alcohol. If the pack rests below 10.8V under load, contact resistance is the likely culprit. A full discharge-recharge cycle will confirm whether the issue is the pack or the connector seat.