Fodsports M1S Pro Replacement Battery 3.7V 800mAh

Fodsports M1S Pro — 3.7V Li-Polymer Replacement Battery (LFT802540)

This 3.7V, 800mAh Li-Polymer cell replaces the original LFT802540 battery in the Fodsports M1S Pro Bluetooth headset. It restores power to the audio and wireless connectivity functions when the original cell has degraded or stopped holding a charge. Dimensions are 41.90 x 24.50 x 8.00mm — confirm against your existing cell before fitting.

• M1S Pro fit: The M1S Pro runs audio decoding and Bluetooth radio from a single cell. Both draw simultaneously during calls, so the cell voltage rail must stay stable under combined load — this replacement matches the original voltage and connector to maintain that balance.
• Bench tested on actual hardware: We cycled this cell under combined Bluetooth radio and audio draw. The BMS held voltage within spec throughout and cut off cleanly at the lower threshold — no premature dropout was triggered.
• First charge after fitting: Charge the M1S Pro to full before making a call. The headset's talk-time estimate is logged during that first full cycle — skipping it causes the indicator to report inaccurate charge levels for the first several uses.

Why the M1S Pro cuts out mid-call even with a charged battery

The M1S Pro draws from one cell to run both audio processing and the Bluetooth radio at the same time. Under that combined load, a degraded or newly fitted cell can sag below the BMS cutoff threshold before the displayed charge level suggests it should. The BMS reads actual cell voltage — not the percentage shown on a paired device. If the headset cuts mid-call, check the resting voltage of the cell; it should read above 3.6V after a full charge cycle.

Talk time shorter than expected on the first few charges

A new Li-Polymer cell does not deliver full capacity on the first charge. Internal resistance is slightly elevated until the cell has been through three to five full charge and discharge cycles. During this period the M1S Pro will cut off earlier than the rated capacity implies. Run the headset through several complete cycles — charge fully, use until the low-battery alert triggers, then recharge — and talk time will increase to the cell's rated 800mAh output.