JBL KMC 600 Wireless Mic Compatible Battery TD0535 3.7V 3400mAh

JBL KMC 600 — 3.7V Li-ion Replacement Battery (TD0535)

This is a 3.7V 3400mAh Li-ion battery for the JBL KMC 600 wireless microphone. It replaces part number TD0535 in the transmitter body. Voltage and capacity match the original specification exactly.

• KMC 600 transmitter fit: The KMC 600 uses a single-cell Li-ion pack at 3.7V nominal. The BMS in this transmitter monitors cell voltage directly — a cell with the wrong voltage profile will cause the unit to refuse to power on or report a fault before the battery is even depleted.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a KMC 600 transmitter body. The BMS accepted the cell without error flags, held lock at the RF stage through full charge drawdown, and the low-battery indicator triggered at the expected voltage threshold.
• Transmitter storage between gigs: If the KMC 600 sits unused for several weeks, discharge the cell to around 50% before storing — leaving it fully charged accelerates lithium-ion calendar aging faster than cycling does, which affects peak voltage delivery on your next live set.

Why the KMC 600 drops audio mid-performance on a new battery

A freshly installed cell can still cause mid-show dropouts if the battery contacts inside the transmitter have oxidation or debris preventing a solid connection. Under the sustained current draw of active RF transmission, a poor contact creates momentary voltage sag that the BMS reads as a low-cell condition. The transmitter briefly cuts output to protect the cell — that's the dropout you hear through the PA. Clean the contact pins with a dry cotton swab before installing any new cell.

Receiver losing lock on transmitter after battery swap

Swapping the battery in the KMC 600 transmitter cuts power to the RF stage entirely. When power is restored, the transmitter re-initialises its RF link from scratch. If the receiver doesn't automatically reacquire, it's still holding the last sync state from the dead cell. Power cycle the receiver after any battery swap — turn it off, wait five seconds, turn it back on — and the RF handshake will re-establish at the correct channel and frequency pair.