Plantronics CS70 Replacement Battery 3.7V 140mAh PA-PL003

Plantronics CS70 / Voyager Pro Series — 3.7V Li-Polymer Replacement Battery (PA-PL003)

This 3.7V, 140mAh Li-Polymer cell replaces the original battery in the Plantronics CS70, CS70N, Voyager Pro, and Voyager Pro+ wireless DECT headsets. It fits the compact battery bay on these office headsets and connects via the original BMS circuit. Use the Capacity field figure — 140mAh — as the reference for this pack.

• CS70 and Voyager Pro compatibility: These models share the same 3.7V cell footprint, connector pin-out, and BMS handshake protocol. Swapping the cell between them works because the base station communicates charge state through the same circuit logic across this headset line.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on the CS70 base station. The BMS handshake completed on the first dock, and charge current tapered correctly at top-of-charge — no error flags from the base.
• First dock cycle on the CS70 base: Seat the headset in the base station and leave it for a full uninterrupted charge cycle before taking any calls. The base needs that cycle to log the new cell and begin tracking talk-time accurately — skipping it leaves the charge indicator unreliable for the first few uses.

Base station showing full charge but headset cuts off after short use

A new Li-Polymer cell ships at storage voltage — typically around 3.6V — not at full 3.7V charge. The base station can misread this as a topped-up pack and stop charging early. The headset then draws down from a partial state and cuts out sooner than expected. One complete dock cycle corrects the base's reference point and the problem clears after that first full charge.

Headset cutting out mid-call on a new battery

The CS70 and Voyager Pro combine audio processing and DECT radio transmission simultaneously during a call. That combined draw is higher than idle current and can trigger a BMS undervoltage cutoff if the cell voltage sags below threshold mid-transmission. On a brand-new cell, this settles after three to five charge cycles as the Li-Polymer chemistry stabilises its internal resistance. If cutouts persist past five cycles, check that the headset contacts and base cradle pins are clean and making firm contact.