About this replacement
Panasonic EY3653 / EY3654 Series — 7.2V Ni-MH Replacement Battery (EY9065)
This is a 7.2V 3300mAh Ni-MH replacement battery for the Panasonic EY3653, EY3653CQ, EY3654, and EY3654CQ cordless drill/drivers. It replaces OEM part numbers EY9065, EY9066B, BCP-EY9065, and PA-724. Capacity is sourced from the product specification — 3300mAh / 23.76Wh.
- EY3653 and EY3654 platform fitment: Both models share the same 7.2V battery bay, connector pinout, and charge termination logic. A single pack covers both variants, including the CQ sub-models, because the voltage rail and physical latch are identical across the series.
- Bench tested on actual hardware: We cycled this pack through a Panasonic 7.2V charger and monitored the delta-peak termination signal. The BMS responded correctly at full charge cutoff, and cell balance across the Ni-MH stack held within spec across three discharge cycles.
- First-use load conditioning on the EY3653: On first use, run the drill at half load — light fastening, no torque-heavy applications — for two full charge-discharge cycles. This lets the pack's charge management system profile the motor inrush current before you push maximum torque settings.
BMS cutoff on motor-start inrush in the EY3653
When you pull the trigger on a cordless drill, the motor draws a short inrush spike — often three to five times the running current — before it reaches operating speed. On Ni-MH packs, if the cells are cold or partially discharged, internal resistance rises and the voltage rail can dip sharply during that spike. The BMS interprets this as an overcurrent event and cuts the output to protect the cells. Warming the pack to room temperature before use and avoiding a deeply discharged state are the two most direct ways to prevent nuisance trips on the EY3653.
Drill bogs under load mid-task and recovers when you release the trigger
This is voltage sag — not a failed battery. Under sustained torque, the cells cannot deliver current fast enough to hold the 7.2V rail steady, so motor speed drops. Release the trigger, the rail recovers, and the drill feels fine at idle. Check the battery contacts first: oxidised or bent terminals add resistance and make sag worse. If contacts are clean and the symptom persists across a freshly charged pack, the cells are capacity-faded and the pack needs replacement. A healthy pack under load should hold above 6.0V at the rail.