Clarity C4205 Cordless Phone Compatible Battery 3.6V 700mAh

Clarity C4205 / C600 / W425 — 3.6V Ni-MH Replacement Battery

This is a 3.6V 700mAh Ni-MH replacement battery for the Clarity C4205, C600, and W425 cordless phone handsets. All three models share the same battery bay geometry and voltage rail, so one pack covers the full set. Swap it in when the original pack no longer holds a charge between calls.

• C4205, C600, and W425 compatibility: These three Clarity handsets run off the same 3.6V three-cell Ni-MH configuration with identical connector pinout and bay dimensions (45.60 × 31.30 × 10.60mm). The BMS on each model accepts the same charge termination signal, so no pairing or handshake step is required after installation.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Clarity handset base station and confirmed stable voltage delivery across standby and active RF transmission states. The BMS showed no false low-battery flag after the first full conditioning cycle.
• First charge after installation: Seat the handset in the base immediately after swapping the battery and leave it for a full 16 hours before first use. Clarity cordless bases use a slow trickle charge optimised for Ni-MH — cutting that first cycle short leaves the pack 15–20% below rated capacity from the start.

Talk time shorter than expected on the C4205 after a new battery

Ni-MH cells in cordless phone packs don't reach rated capacity on the first charge cycle — this is normal cell chemistry, not a fault. The C4205 base delivers a slow 100mA trickle charge, which means the first three to five full cycles are needed before the cells reach their 700mAh ceiling. Each cycle should show a measurable improvement in talk time. By cycle five, capacity should stabilise at or near the rated 700mAh (2.52Wh).

Base station won't start charging after the battery swap

Ni-MH packs can self-discharge during storage, sometimes dropping below the voltage floor the Clarity base uses to detect a valid battery. If the base shows no charge light or an error state, the pack voltage is likely below 3.0V. Remove the battery, let it rest at room temperature for 10 minutes, then reseat the handset firmly in the base — some bases require full contact on all three charge pins to initiate the charge cycle. If the charge light still won't trigger, measure across the battery terminals with a multimeter; a reading below 2.8V means the pack needs a single slow top-up via a universal Ni-MH charger set to 100mA before the base will accept it.