Plantronics CT14 80639-01 Replacement Battery 2.4V 700mAh

Plantronics CT14 — 2.4V Ni-MH Replacement Battery (80639-01)

This is a 2.4V, 700mAh Ni-MH replacement battery for the Plantronics CT14 DECT cordless headset. It fits the CT14 headset unit directly and restores wireless communication between the headset and its base station. OEM part numbers covered: 80639-01, 81087-01, and 81087-02.

• CT14 DECT headset compatibility: The CT14 runs a 2.4V cell that powers both the audio driver and the DECT radio simultaneously. These two loads share the same cell, so the battery must meet the combined draw without sagging — this pack matches the original cell format, connector, and voltage rating exactly.
• Bench tested on actual hardware: We ran this pack through the CT14 base station charge cycle and confirmed the BMS handshake completes normally. The base station accepted the new cell without error and cycled through to a full-charge indication.
• First-cycle base station logging: Place the headset in the base station and run a full charge cycle before taking any calls. The CT14 base logs the new cell during this first cycle — until it does, the talk-time estimate on the base will not reflect actual capacity.

Base station not recognising the new pack after swap

The CT14 base station uses a BMS handshake to identify and begin charging a new cell. If the headset is docked and the charge indicator does not activate within a few minutes, the handshake has not completed. Remove the headset, wait 10 seconds, and re-dock it firmly — the contacts on the CT14 headset are small and misalignment is common. If the indicator still does not respond, check that the cell voltage has not dropped below the base station's detection threshold, which sits around 1.8V total for the two-cell pack.

Headset cuts out mid-call on a new battery

A freshly installed Ni-MH cell does not always deliver full capacity on the first few cycles — this is normal chemistry behaviour, not a fault with the pack. The DECT radio and audio driver together pull enough current to trigger a low-voltage cutoff if the cell has not yet conditioned. Run three to five full charge-and-use cycles through the base station and capacity will stabilise. If cutouts continue past five cycles, measure resting voltage at the cell terminals — it should read at or above 2.4V after a full charge.