Plantronics CT901HS Replacement Battery 3.6V 1300mAh

Plantronics CT901HS — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 1300mAh Ni-MH battery for the Plantronics CT901HS cordless phone headset. It replaces the original rechargeable cell when the existing pack no longer holds charge. Drop voltage, short talk sessions, or a base station that never shows a full-charge indicator are the usual signs it's time to swap.

• CT901HS fit: The CT901HS runs a 3.6V Ni-MH cell with a specific physical footprint — 50.57 x 42.47 x 14.35mm. This battery matches that envelope and the voltage rail the headset's charging circuit expects. A mismatched voltage will cause the base to reject the pack or fail to terminate the charge correctly.
• Bench tested on actual hardware: We cycled this pack through the CT901HS base station and confirmed the BMS accepted the charge, reached termination, and released correctly. Voltage held stable across the headset's transmit and standby draw profiles with no mid-use cutoff.
• First-charge protocol for Ni-MH headsets: After installing, seat the headset in the base and leave it for a full 16 hours before first use. Ni-MH cells shipped in a partially discharged state won't reach rated capacity on a short top-up charge — the slow first cycle is what conditions the pack to its full 1300mAh.

Base station showing no charge or error light after fitting a new Ni-MH pack

Ni-MH batteries lose voltage during storage. If the pack sits long enough before use, its open-circuit voltage can drop below the threshold the CT901HS base expects before initiating a charge cycle. The base sees the low voltage and reads it as a fault rather than an empty cell. To recover, briefly charge the pack in a standalone Ni-MH charger at a low rate — even 15 minutes is enough to bring the voltage up to a level the base will accept and then charge normally.

Talk time shorter than the original battery for the first few sessions

This is a Ni-MH characteristic, not a faulty battery. Fresh Ni-MH cells need three to five full charge-discharge cycles before the chemical structure inside the cell stabilises and delivers rated capacity. Talk time will be noticeably shorter in the first few sessions and will extend with each subsequent full cycle. Run the headset until the low-battery indicator triggers, return it to the base for a full charge, and repeat — by cycle five, the pack should be at or near its rated 1300mAh.