NEC Flexiphone 100 Replacement Battery 3.6V 600mAh Ni-MH

NEC Flexiphone 100 / Flexiphone 50 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 600mAh Ni-MH rechargeable battery for the NEC Flexiphone 100 and Flexiphone 50 cordless handsets. It slots into the battery compartment and powers the handset during calls and standby when out of the base. Capacity is 600mAh (2.16Wh), matching the original pack.

• Flexiphone 100 and 50 compatibility: Both models share the same 3.6V single-cell NiMH bay, connector orientation, and charge termination voltage. One battery fits both handsets.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a NiMH-compatible tester. The BMS accepted a full charge without thermal event and held voltage within the expected range across three consecutive cycles.
• First charge after installation: Place the handset in the base cradle for a continuous 16-hour charge before first use. NiMH cells in cordless phones reach rated capacity through a slow initial charge — skipping this step leaves the pack under-formed and cuts apparent talk time short.

Base station showing no charge or error light with a new NiMH pack

NiMH batteries lose voltage during storage. If the pack has been sitting in a warehouse, its resting voltage can drop low enough that the base station's charge controller doesn't recognise it as a valid battery. The base expects to see a cell above roughly 1.0V per cell — at 3.0V total — before initiating a charge cycle. If the error light stays on, remove the handset, wait 30 seconds, and re-seat it firmly so the charge contacts close fully. If that doesn't clear it, a brief trickle from a compatible NiMH charger at 60mA for 15 minutes can raise the pack voltage enough for the base to accept it.

Range drops mid-call after installing a replacement battery

DECT handsets draw a burst of current every time the RF module transmits. A NiMH pack that hasn't been fully conditioned has higher internal resistance, which causes voltage to sag under that transmit load. The handset interprets the sag as a low-battery state and reduces transmit power to protect the cell — shrinking range as a result. This typically resolves after three to five full charge-and-use cycles, which lower internal resistance and bring the pack to rated capacity. If range is still poor after five cycles, check that the handset is fully seated in the base each time — a poor contact connection produces a partial charge rather than a full one.