Black & Decker A12 12V Cordless Drill Replacement Battery 3000mAh

Black & Decker BD12PSK Series 12V Ni-MH 3000mAh Replacement Battery (A12 / HPB12 / FSB12)

This is a 12V, 3000mAh Ni-MH replacement battery pack for the Black & Decker BD12PSK cordless drill/driver and a wide range of compatible 12V Black & Decker tools. It replaces OEM part numbers including A12, HPB12, FSB12, FS120B, and A12EX among others. Voltage and cell chemistry match the original pack exactly.

• BD12PSK and compatible 12V platform: These models share a common 12V cell architecture, the same connector footprint, and a matching BMS communication protocol. Swapping the pack requires no modification the charger and tool handshake proceed identically to the original.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on a BD12PSK drill, confirming BMS engage and disengage at correct voltage thresholds. Overcurrent protection tripped cleanly on simulated stall loads and reset without fault.
• Motor inrush conditioning on first use: On first use, run the drill at half load for two full cycles before maximum torque applications. This allows the BMS to profile the motor’s inrush current signature and set overcurrent thresholds before you hit high-resistance fastening work.

BMS cutoff on trigger-pull inrush in the BD12PSK

When you pull the trigger on a cordless drill, the motor draws a current spike often three to five times the running current for the first fraction of a second. On a new or recently stored Ni-MH pack, the BMS may not yet have a calibrated threshold for that spike. It can interpret the inrush as an overcurrent fault and cut power before the motor even turns. The fix is gradual conditioning over two partial-load cycles, which lets the BMS log the motor’s start signature and distinguish it from a genuine fault event. After conditioning, trigger-pull cutouts on the BD12PSK are rare under normal use.

Tool bogs under load but runs fine unloaded

If the BD12PSK loses speed or torque the moment it meets resistance screws stall, holes bog but spins freely with no load, the likely cause is voltage sag from high rail contact resistance or an unconditioned pack. Ni-MH cells drop internal voltage sharply under load when they haven’t been through a proper break-in cycle. Check the battery contact rails on the tool and pack for oxidation clean them with isopropyl alcohol and a lint-free cloth. After cleaning, run two full charge-discharge cycles and test under load again; resting voltage should hold above 10.8V through a standard driving sequence.