Bose AHB501220P Bluetooth Headset Replacement Battery 3.7V 80mAh

Bose Bluetooth Headset Series 1 / Series 2 — 3.7V Li-Polymer Replacement Battery (AHB501220P)

This is a 3.7V, 80mAh Li-Polymer cell (AHB501220P) for the Bose Bluetooth Headset Series 1 and Series 2. It fits the BTL1 and BTL2 platforms. When the original cell degrades and the headset drops off calls or refuses to hold charge, this cell restores full function.

• BTL1 and BTL2 platform fit: The Series 1 and Series 2 share the same battery bay geometry, connector pin-out, and 3.7V nominal rail. Both platforms use the same BMS handshake sequence with the base station, so one cell covers both without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the BTL platform. The BMS accepted the new pack without error flags, the base station logged the cell correctly, and charge termination triggered at the expected cutoff voltage.
• Base station pairing on first install: Seat the headset in the base station and let it complete one full charge cycle before using it on a call. The base station uses that first cycle to calibrate its fuel gauge against the new cell — skipping it causes inaccurate charge indicators.

Wireless headset cutting out mid-call on a new battery

The BTL headset draws from two loads simultaneously during a call — the audio codec and the Bluetooth radio. On a freshly installed cell that has not completed its first conditioning cycle, the combined draw can push the cell voltage below the BMS cutoff threshold momentarily, triggering a shutdown. This looks like a hardware fault but it is a cell state issue. Running three to five full charge-discharge cycles through the base station brings the cell to rated delivery capacity and eliminates the sag. After conditioning, the cell holds above 3.5V under combined load without tripping the cutoff.

Base station shows full charge but headset cuts off after a few seconds

This happens when the replacement cell arrives at storage voltage — typically around 3.6V — and the base station misreads it as already charged. The fuel gauge reports 100% but the cell has not gone through a proper charge cycle from the base's charging circuit. Pull the headset from the base, power it on until it shuts off from depletion, then reseat it and charge uninterrupted to full. The base will then run a proper charge cycle and the voltage reading will be accurate.