About this replacement
Sena SMH-10S / SMH-20S — 3.7V Li-Polymer Replacement Battery (YP802542P)
This is a 3.7V, 650mAh Li-Polymer cell (YP802542P) for the Sena SMH-10S and SMH-20S helmet-mounted Bluetooth headsets. Both models use the same compact cell to power Bluetooth audio, intercom, and music streaming. When the original cell degrades and talk time drops sharply, this is the direct replacement.
- SMH-10S and SMH-20S compatibility: Both headsets share the same YP802542P cell format, voltage rail, and connector. The BMS in each unit uses the same handshake protocol, so no firmware differences affect fitment between the two models.
- Bench tested on actual hardware: We cycled this cell through the SMH-10S at combined Bluetooth audio and intercom draw. The BMS held the cutoff voltage correctly and the unit reported charge status accurately after a full conditioning cycle.
- First-use charging on SMH headsets: Seat the headset in the charging cradle and run a complete charge cycle before making a call. The SMH series logs the new cell through the cradle — skipping this step causes the talk-time indicator to read incorrectly for the first several uses.
Why the SMH-10S cuts out mid-call even with a charged battery
The SMH-10S draws current from two simultaneous loads — the Bluetooth radio and the audio amplifier. Under that combined draw, a degraded or storage-voltage cell sags below the BMS cutoff threshold and the unit shuts off. This looks like a software fault but is a voltage issue. A new cell at full charge resolves this, provided the first full cradle cycle has been completed to let the BMS calibrate its discharge curve.
Headset shows full charge but shuts off after a short session
Replacement cells ship at storage voltage — typically 3.6–3.8V — not at full charge. The SMH headset reads this as a charged state and reports a full indicator, but the actual usable capacity is not yet available. The fix is a complete charge cycle in the cradle before first use. After one full cycle, the charge indicator and actual runtime will align. If the problem persists past three full cycles, check cradle contact pins for corrosion.