Firestorm BD14PSK 9.6V Ni-MH Compatible Battery 2500mAh

Firestorm BD14PSK Series — 9.6V Ni-MH Replacement Battery (FSB18)

This is a 9.6V, 2500mAh Ni-MH battery pack for the Firestorm BD14PSK cordless drill and related models including the FS1200D, FS1200D-2, and FS1202BN. It replaces OEM part numbers FSB18, FSB12, FS18BX, FS120B, and others in that family. The pack slots directly into the tool's battery bay and connects via the original terminal block.

• BD14PSK and FS1200D series compatibility: These models share the same 9.6V battery bay, terminal layout, and BMS handshake requirements. A single pack design covers the full range because the voltage rail and connector geometry are identical across this platform.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on a BD14PSK-class drill, confirmed the BMS accepted charge from the OEM charger without error, and verified the terminal contacts held clean voltage delivery through sustained trigger pulls.
• Ni-MH memory conditioning on first use: Run the drill at moderate load — not full-torque fastening — for the first two charge cycles. Ni-MH cells develop a memory effect if the first few cycles are too shallow or too aggressive, and a gradual break-in lets the chemistry reach its rated 2500mAh capacity consistently.

BMS cutoff on BD14PSK motor-start inrush surge

When a cordless drill motor starts from rest, it draws a brief current spike — often three to five times the running current — before the motor reaches speed. On a 9.6V Ni-MH pack, the BMS overcurrent threshold is set tight enough that a degraded or deeply discharged cell cluster can trip the cutoff on that inrush spike alone. The drill cuts out instantly on trigger pull and won't restart until the BMS resets. A full charge to 9.6V at the pack terminals before first use clears most of these false trips.

Drill bogs under load but runs fine at idle

If the drill spins freely with no bit but slows noticeably when driving screws, the cause is usually voltage sag — the pack voltage drops under load because internal cell resistance has risen. Ni-MH packs are particularly susceptible after repeated shallow cycling, where cells never fully discharge and capacity-robbing stratification builds up. Check the terminal contacts for oxidation first — dirty contacts add resistance and amplify sag. If contacts are clean, run two full discharge-recharge cycles to partially recondition the cells and confirm the pack voltage holds above 8.5V under load.