Nikon NP55 Replacement Battery 6V 4200mAh Ni-MH

NiKon NP55 / NP66 / NP77 Series — 6V Ni-MH Replacement Battery

This is a 6V 4200mAh Ni-MH replacement battery for NiKon cameras using the NP55, NP66, NP66H, and NP77 battery format, plus 38 additional compatible models. It slots into the same battery compartment as the original cell and restores full camera operation. Voltage and physical form factor match OEM spec.

• NP55 / NP66 / NP77 platform fit: These models share the same 6V rail and physical housing dimensions, which is why one cell covers the full range. The connector orientation and BMS communication protocol are consistent across this NiKon battery family, so the same cell works across all listed bodies without adaptation.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on NP66-compatible camera bodies. The BMS accepted the cell on the first charge cycle via OEM charger, and current draw during continuous shooting remained stable across the discharge curve with no mid-session cutoff.
• First-cycle charge protocol on NiKon bodies: NiKon camera bodies in this series calibrate their battery-remaining display during the first full charge cycle. Run the first charge inside the camera body or OEM charger — not a third-party charger — so the body correctly maps the cell's discharge curve to its percentage indicator from the start.

Flash recycling slowdown on a new NP66 cell approaching end of charge

As the NP66 cell drops below roughly 5.4V under load, the flash capacitor recharge current sags noticeably. The camera body still shows battery remaining, but the recycling interval between flash shots stretches out. This is normal Ni-MH voltage sag behaviour — the cell is not failing. It is a sign the cell is in the final 10–15% of its discharge cycle. Recharge the cell before a flash-heavy shoot to keep recycling times consistent.

Battery percentage jumping erratically on the NiKon body display

NiKon bodies in this series map percentage thresholds to specific voltage points calibrated for the original OEM cell's discharge curve. A replacement Ni-MH cell with a slightly different curve can cause the display to skip from 80% to 40% without warning. This is a display mapping issue, not a cell fault. Run two or three full charge-discharge cycles through the camera body — most NiKon bodies re-map thresholds after repeated cycles and the readout stabilises around the 5.8V midpoint.