Philips TAPH805 LFT603040 Compatible Battery 3.7V 680mAh

Philips TAPH805 — 3.7V Li-Polymer Replacement Battery (LFT603040)

This is a 3.7V, 680mAh Li-Polymer battery for the Philips TAPH805 Bluetooth wireless headset. It replaces part number LFT603040 when the original cell has degraded through repeated charge cycles. The TAPH805 draws from this cell to power both the audio driver and the Bluetooth radio simultaneously.

• TAPH805 platform fit: The TAPH805 uses a single-cell Li-Polymer pack with a proprietary connector and BMS handshake specific to this headset. This replacement matches the voltage rail, connector pinout, and cell dimensions (42.60 × 29.40 × 6.00mm) the headset expects.
• Bench tested on actual hardware: We cycled this battery under combined Bluetooth radio and audio playback load. The BMS held the discharge curve steady and triggered protection cutoff at the correct low-voltage threshold without nuisance tripping.
• First charge in the base station: Place the TAPH805 in its base station and run a complete charge cycle before taking a call. The base station logs the new cell during this cycle, and the talk-time indicator will not read accurately until that handshake is complete.

Why the TAPH805 cuts out mid-call on a new battery

The TAPH805 runs its audio codec and Bluetooth radio from the same cell. During a call, that combined draw spikes briefly — especially when the radio retransmits on a congested 2.4GHz channel. If the cell has not completed its first full charge cycle, its internal resistance is still elevated, and the voltage can sag just enough to trigger the BMS protection cutoff. Run two or three full charge-discharge cycles through the base station first. After conditioning, the cell's resistance drops and the BMS handles those spikes without cutting the connection.

Base station shows full charge but headset drops off after a few minutes

This happens when a replacement cell arrives at storage voltage — typically around 3.7V — and the base station's charge controller misreads it as already full. The headset then runs on a partially charged cell and cuts off quickly. To fix this, remove the headset from the base, power it on until it shuts down from low battery, then reseat it in the base and leave it for a full uninterrupted charge cycle. Once the base pulls the cell down to the correct charge-start threshold and completes the cycle, the charge indicator and talk time will normalise.