Plantronics M50 Compatible Battery 3.7V 80mAh Li-Polymer

Plantronics M50 / Discovery 650E / Voyager 5200 — 3.7V Li-Polymer Replacement Battery (1704018-0944)

This 3.7V, 80mAh Li-Polymer cell replaces the original battery in the Plantronics M50, Discovery 640E, Discovery 650E, and Voyager 5200 Bluetooth headsets. It is a direct swap for OEM part numbers 1704018-0944 and 71468-01. Dimensions are 30.60 × 10.03 × 4.00mm — match these before fitting if your unit is not listed above.

• M50, Discovery, and Voyager 5200 cell compatibility: These models share a common 3.7V single-cell Li-Polymer architecture, the same connector pinout, and a compatible BMS handshake with the charging circuit — which is why one cell covers all of them.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Plantronics charging cradle. The BMS completed its handshake correctly, the headset registered a charge state, and the protection circuit tripped at the expected low-voltage threshold.
• First charge after fitting: Seat the headset in its charging cradle and leave it for a full uninterrupted charge cycle before use. The cradle needs to complete one full cycle for the firmware's battery gauge to calibrate to the new cell — skip this and the talk-time indicator will read inaccurately for several sessions.

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

A freshly fitted cell ships at storage voltage — typically around 3.6V — not at a full 4.2V charge. The base station LED may flip to green quickly because it reads the cell voltage rather than completing a true charge cycle. The headset then cuts off early because it never held a full charge to begin with. Fix: place the headset in the cradle, ignore the green light, and leave it for a minimum of 90 minutes on first fit to ensure the cell reaches 4.2V.

Talk time shorter than rated across the first few uses

Li-Polymer cells at this capacity class — 80mAh in a compact housing — do not reach full charge retention on cycle one. Internal resistance runs slightly elevated until the cell has been through three to five complete charge and discharge cycles. Audio plus Bluetooth radio draw is sustained and unforgiving on an unconditioned cell. Run three to five full cycles through the cradle before treating the talk-time indicator as accurate.