HC-BA300 Sennheiser IS410 Replacement Battery 3.7V 150mAh

Sennheiser IS410 / RI410 Series — 3.7V Li-Polymer Replacement Battery (HC-BA300)

This 3.7V, 150mAh Li-Polymer cell replaces the HC-BA300 battery in Sennheiser wireless headsets. It fits the IS410, RI410, RS4200, and RR4200 among others. Same voltage rail, same footprint, same connector as the original pack.

• IS410 / RI410 / RS4200 / RR4200 platform: These models share the same compact Li-Polymer cell format, connector pinout, and BMS handshake protocol — so one cell covers the full range without hardware changes.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the IS410 base station. The BMS completed handshake, the charge indicator stepped through correctly, and the headset held audio without voltage dropout under combined DECT radio and audio draw.
• Base station conditioning on first use: Seat the headset in the base station and let it complete a full uninterrupted charge cycle before taking a call. DECT headsets log the new cell during that first cycle — until it completes, the talk-time estimate shown on the base will read low or erratically.

Base station not recognising the new pack after fitting

The IS410 base uses a BMS handshake to verify the cell before beginning a charge cycle. If the replacement arrives at storage voltage — typically around 3.6V — the base may not initiate charging on the first seat. Remove the headset, wait 10 seconds, and reseat it firmly. If the charge indicator still does not step through, briefly connecting a compatible USB charger directly can nudge the cell voltage high enough for the base to recognise the pack and take over the charge cycle.

Headset cutting out mid-call on a fresh battery

The IS410 draws simultaneously from the audio circuit and the DECT radio transmitter. On a cell that has not completed its first few conditioning cycles, this combined load can pull instantaneous voltage below the BMS cutoff threshold even when the headset shows a charge. The BMS interprets the sag as a depleted cell and trips protection. Run three full charge-discharge cycles through the base station — by cycle three, internal resistance drops enough that the voltage sag under combined draw stays above the 3.0V cutoff.