Sennheiser SK9000 Replacement Battery 3.7V 2200mAh Li-ion

Sennheiser SK9000 Bodypack Transmitter — 3.7V Li-ion Replacement Battery (56429 701 098)

This is a 3.7V, 2200mAh (8.14Wh) Li-ion replacement battery for the Sennheiser SK9000 wireless bodypack transmitter. It fits the SK9000 series used in live performance, broadcast, and production environments. Swap it when your original cell no longer holds charge through a full set or session.

• SK9000 series compatibility: The SK9000 bodypack runs audio processing and UHF transmission from a single cell. This battery matches the voltage rail, physical footprint (61.68 × 41.78 × 14.60mm), and connector orientation the transmitter expects. The BMS on these packs communicates state-of-charge back to the transmitter — incorrect voltage or a mismatched cell trips a charge fault before the first cycle completes.
• Bench tested on actual hardware: We cycled this cell through the SK9000's BMS handshake and confirmed clean charge acceptance at 3.7V nominal. The protection circuit responded correctly to simulated overdischarge — cutoff triggered at the expected threshold with no latching fault.
• First-charge protocol for SK9000: Insert the battery and dock the transmitter in its charger for a full uninterrupted charge before the first use. The SK9000's firmware calibrates its fuel gauge against the new cell during this cycle — skipping it causes the transmitter to misread state-of-charge for several sessions.

Why the SK9000 base station shows a charging error with a new battery

The SK9000 charger reads BMS status data before it starts pushing current. If the replacement cell arrives at storage voltage (typically around 3.6V), the charger may flag an error instead of entering charge mode. This is a handshake timing issue, not a fault with the battery. Remove the transmitter from the dock, wait ten seconds, and re-seat it — this resets the charger's detection cycle and allows the BMS to complete the handshake at 3.7V nominal.

SK9000 cutting out mid-transmission on a new battery

The SK9000 draws simultaneously from the audio circuit and the UHF radio stage — combined current spikes can pull cell voltage below the BMS cutoff threshold if the cell hasn't been fully conditioned. This usually appears as a hard dropout rather than a gradual fade. On the first three to five cycles, peak capacity hasn't stabilised, so the protection circuit trips earlier than expected under combined load. Run three full charge-discharge cycles through normal use and the dropout threshold should shift to the correct voltage floor.