Sennheiser 508494 Replacement Battery 3.7V 1000mAh Li-ion

Sennheiser 508494 / 508497 Series — 3.7V Li-ion Replacement Battery (14500CY-850)

This is a 3.7V, 1000mAh Li-ion replacement cell for Sennheiser wireless microphone transmitters using OEM part number 14500CY-850. It fits the 508494, 508497, RX 63, and RX XLR body packs, among others. Same voltage, same form factor as the original — slots directly into the transmitter battery compartment.

• 508494 / 508497 transmitter compatibility: These body packs share the same 14500-format Li-ion cell and BMS handshake threshold. Swapping to a cell outside the 3.7V nominal range causes the transmitter to flag a fault or refuse to power on entirely.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a 508494 transmitter body. The BMS accepted the cell without fault codes, and the RF link held stable across the full discharge curve.
• Transmit-draw awareness: Wireless body packs pull current in sharp bursts during RF transmission. A cell with weak internal resistance will sag under those bursts, causing audio artefacts before the battery indicator shows any warning. This cell's impedance stays low enough through the discharge cycle to avoid that early sag.

Why a new 14500CY-850 cell can still cause audio dropouts on the 508494

A freshly installed cell that ships partially discharged can sit just below the transmitter's minimum voltage threshold under load, even if the indicator shows adequate charge. The 508494's BMS monitors real-time voltage under transmit draw — not resting voltage — so a cell at 3.5V open-circuit may dip to 3.3V during an RF burst and trigger a momentary mute. Charge the replacement cell fully before first live use. A resting voltage of 4.1–4.2V confirms it is ready for transmitter operation.

Receiver losing RF lock immediately after a battery swap

When the transmitter loses power — even briefly during a cell swap — it clears its active RF handshake with the paired receiver. The receiver holds the last known channel but waits for the transmitter to re-announce itself on power-up. If the new cell seats with poor contact on the spring terminal, the transmitter may pulse power rather than boot cleanly, and the receiver never receives a valid sync signal. Check that the cell is fully seated and the terminal spring has tension, then power cycle the transmitter fully. The receiver should re-lock within a few seconds of a clean transmitter boot.