Panasonic EY9180B 9.6V Ni-MH Replacement Battery for EZ571

Panasonic EZ571 / EY6282EQK Series — 9.6V Ni-MH Replacement Battery (EY9180B)

This is a 9.6V Ni-MH battery rated at 3300mAh (31.68Wh), built to fit the Panasonic EZ571 cordless drill/driver and related models in the EY-series lineup. It replaces OEM part numbers EY9180B and EY9180. The pack slots into the same battery bay and uses the same connector geometry as the original.

• EZ571, EY6282EQK, EYN595, EY9184 compatibility: These models share the same 9.6V rail, identical battery bay dimensions, and the same three-pin connector layout — which is why one pack covers the group. No adapter needed.
• Bench tested on actual hardware: We ran this pack through a full charge-discharge cycle on the EZ571 platform. The BMS held stable through repeated trigger pulls and did not trip on motor-start inrush at no-load RPM.
• First-use load conditioning: Run the drill at half load for two cycles before applying full torque. This lets the BMS log real inrush current from the motor before it sets overcurrent thresholds — prevents nuisance cutoffs on heavy fastening tasks later.

BMS cutoff on motor-start inrush in the EZ571

The EZ571 motor draws a spike of current the instant the trigger is pulled — sometimes two to three times the running current. On a new or cold Ni-MH pack, the BMS may read that spike as an overcurrent event and cut the output rail. This is more likely in the first few cycles before the BMS has profiled the motor's inrush signature. Running two break-in cycles at reduced load gives the protection circuit enough data to allow full-current starts without tripping.

Tool bogs under load even with a charged pack

If the drill feels weak or slows noticeably under torque, the most likely cause is voltage sag — the terminal voltage drops under load due to high contact resistance at the battery rail. Check the brass contacts on both the pack and the tool body for oxidation or debris. Clean contacts with isopropyl alcohol and a contact brush. If the pack reads above 10.5V off-load but sags below 8.5V on trigger pull, the cells are cycling correctly and the fault is at the connection, not the chemistry.