Panasonic EZ902 2.4V Ni-MH Replacement Battery 1500mAh

Panasonic EZ502 / EZ503 Series — 2.4V Ni-MH Replacement Battery (EZ902)

This is a 2.4V, 1500mAh Ni-MH replacement battery for the Panasonic EZ502 and EZ503 compact drill/drivers, along with the EZ581, EY3652, and over 20 additional models in this series. It replaces OEM part numbers EZ902, EY9021, EY9021B, EY903, EY903B, and several others. Physical dimensions are 100.19 x 39.38 x 38.38mm — check your original pack before ordering if space is tight.

• EZ502 / EZ503 platform fit: These models share the same 2.4V single-cell architecture, connector pinout, and pack housing — one battery SKU covers the range without modification.
• Bench tested on actual hardware: We cycled this pack on the EZ502 platform through repeated trigger pulls and monitored cell voltage recovery between draws. The Ni-MH chemistry held voltage flat through moderate load without the BMS tripping on inrush.
• First-cycle load conditioning: Run the drill at half torque for two full discharge-charge cycles before driving at maximum torque. This lets the internal cell resistance stabilise so the tool's overload protection doesn't trip early on hard fasteners.

Why the EZ502 cuts out instantly on trigger pull

The EZ502 motor draws a sharp inrush current the moment the trigger engages — this spike is 3 to 5 times the steady running current. On a degraded or deeply discharged Ni-MH pack, internal resistance is high enough that the voltage rail collapses under that spike. The tool's protection circuit reads it as a fault and kills output before the motor even spins. A fresh, properly conditioned pack with low internal resistance handles the inrush without dropping below the cutoff threshold.

Charger not recognising a new pack after storage

Ni-MH packs stored for extended periods can self-discharge below the charger's acceptance voltage — the charger sees the low voltage and refuses to begin a charge cycle. This is not a dead pack. Place the battery in the charger and check for a blinking or error light; if the charger won't initiate, try a brief trickle from a compatible 2.4V source to raise the cell voltage above 2.0V. Once the pack crosses the charger's threshold — typically around 2.0–2.1V per cell — the standard charge cycle will engage normally.