About this replacement
Panasonic EY6107 / EY6470NQ Series — 12V Ni-MH 2100mAh Replacement Battery (EY9200)
This is a 12V Ni-MH replacement battery rated at 2100mAh, built to fit the Panasonic EY6107 cordless drill/driver and compatible 12V platform models including the EY6470NQ and EY6903NQ. It replaces OEM part numbers EY9200, EY9200B, EY9101, EY9106, EY9107, and PA-1204N, among others. The pack slots into the same bay as the original and draws from the same 12V rail these tools were built around.
- 12V Panasonic platform fit: The EY6107, EY6470NQ, EY6903NQ, and EY6506NQ share a common 12V battery interface with the same terminal arrangement and latch geometry. Any pack that fits one will fit the others — the voltage rail and connector spec are identical across this generation of Panasonic 12V tools.
- Bench tested on actual hardware: We cycled this pack through repeated trigger-pull loads on the EY6107 platform, monitoring cell voltage under motor-start inrush. The pack held stable across cold starts without tripping overcurrent cutoff at normal drilling torque.
- Break-in on Ni-MH packs: Run the drill at half load for the first two cycles before pushing full torque or driving long fasteners. Ni-MH cells reach rated capacity after two or three full discharge-charge cycles — pushing maximum load immediately on a new pack can cause premature voltage depression in the cells.
Voltage depression in Ni-MH packs after shallow cycling
Ni-MH cells develop voltage depression — sometimes called the memory effect — when repeatedly charged after only partial discharge. The pack appears full but cuts out early under load because the usable voltage window has narrowed. On the EY6107, this shows up as the drill losing torque halfway through a job even though the charger confirmed a full charge. Running three full discharge cycles down to approximately 10.8V before recharging resets the cell baseline and restores usable capacity.
Charger not recognising the pack after storage
Panasonic's 12V charger uses a voltage handshake to confirm pack condition before beginning a charge cycle. If cells have self-discharged below roughly 9V during storage, the charger may reject the pack entirely — no lights, or an immediate fault indicator. Connecting the pack to the charger for 15–20 seconds, removing it, and reconnecting can prompt re-recognition on some units. If the charger still refuses the pack, check cell voltage with a multimeter — a reading above 9V confirms the pack is recoverable and the charger may need a firmware or contact clean before it will accept it.