Plantronics BackBeat 500 Replacement Battery SP552631SA 3.7V 250mAh

Plantronics BackBeat 500 Series — 3.7V Li-Polymer Replacement Battery (SP552631SA-1S1P-PCM)

This is a 3.7V 250mAh Li-Polymer replacement battery for the Plantronics BackBeat 500, BackBeat 505, BackBeat FIT 505, and 9313SW wireless headsets. It replaces OEM part SP552631SA-1S1P-PCM and restores charging capability when the original cell has degraded. The battery measures 28.20 x 24.80 x 5.00mm and fits the compact cavity in the BackBeat 500 series earcup.

• BackBeat 500, 505, FIT 505, and 9313SW fitment: These models share the same PCM-protected Li-Polymer cell, connector pinout, and BMS voltage thresholds, which is why one part number covers all four. The protection circuit monitors cell voltage and temperature inside the earcup housing.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the BackBeat 500 platform. The BMS handshake completed on the first docking cycle, and the protection circuit tripped correctly at the low-voltage cutoff threshold without any false shutdowns under audio plus Bluetooth radio draw.
• First-cycle docking tip: Place the headset in the charging cradle immediately after installation and let it complete a full charge cycle before use. The BackBeat 500's firmware uses that first cycle to log the new cell's capacity baseline — skipping it causes the battery indicator to read inaccurately for several sessions.

Talk time shorter than expected on a fresh replacement cell

A new Li-Polymer cell does not deliver full capacity on cycle one. The electrochemical interface between the electrolyte and electrode layers needs three to five full charge-discharge cycles before capacity stabilises at the rated 250mAh. During this break-in period, the BackBeat 500 may show shorter use periods than you expect. Run the headset until it triggers the low-battery alert, then dock it for a full charge — repeat this three to five times and capacity will reach its rated level.

Headset cuts out mid-call shortly after battery replacement

The BackBeat 500 draws on two simultaneous loads during a call — the audio driver and the Bluetooth radio. If the replacement cell was stored at low voltage before installation, the BMS can hit its undervoltage cutoff threshold under this combined load even when the indicator shows charge remaining. This is a storage voltage issue, not a faulty cell. Dock the headset, allow a full charge to 4.2V, and the cutouts will stop once the cell is at a proper starting voltage.