National EY9086 9.6V Ni-MH Cordless Drill Replacement Battery

National EZ6181 / EZ6481 Series — 9.6V Ni-MH Replacement Battery (EY9086)

This is a 9.6V 3300mAh Ni-MH battery pack for National cordless drill drivers and handheld power tools in the EZ6181 and EZ6481 series. It replaces OEM part numbers EY9086, EY9086B, EY9182, and EY9182B. Capacity is sourced from product data at 3300mAh (31.68Wh).

• EZ6181 / EZ6481 / EZ6482 platform fit: These models share the same 9.6V battery rail, connector housing, and BMS handshake protocol. One pack covers the full platform. No adapter or modification needed.
• Bench tested on actual hardware: We ran this pack through trigger-pull cycles on an EZ6481 and monitored the BMS under motor-start inrush. The overcurrent protection reset correctly after each spike, and the pack held voltage within the expected rail range across repeated draw events.
• Break-in protocol for Ni-MH cell packs: On first use, run the drill at half load for two full discharge-and-charge cycles before applying maximum torque. Ni-MH cells need cycling to reach rated capacity — the BMS uses early cycles to calibrate overcurrent thresholds against your motor's inrush signature.

BMS cutoff on EZ6181 motor-start inrush surge

When you pull the trigger on a Ni-MH drill driver, the motor draws a short inrush spike — often three to five times the running current. A new pack straight from storage has slightly elevated internal resistance in the cells, which can push the voltage rail low enough during that spike to trip the BMS overcurrent threshold. This is not a defective battery. Running two half-load break-in cycles reduces cell impedance and teaches the BMS what a normal inrush event looks like for your specific motor. After break-in, nuisance trips on trigger pull stop occurring.

Tool bogs under load or loses torque mid-fastener

Voltage sag under sustained load is the most common complaint on worn or new Ni-MH packs used before break-in. When cell impedance is high, heavy torque draws pull the rail voltage down and the motor loses speed. Check the battery contact rails on the tool handle — oxidised or pitted contacts add resistance and make sag worse. Clean the contacts with a pencil eraser, reseat the pack, and confirm the rail reads at least 9.0V under load with a multimeter before suspecting the cells themselves.