Audio-Technica LI-240 Wireless Mic Replacement Battery 7.4V 2600mAh

Audio-Technica ATCS-M60 / ATUC-IRDU — 7.4V Li-ion Replacement Battery (LI-240)

This is a 7.4V, 2600mAh Li-ion replacement for the Audio-Technica LI-240 battery. It fits the ATCS-M60 wireless microphone transmitter and the ATUC-IRDU infrared discussion unit. Voltage and cell count match the OEM spec exactly — no adapters or modifications needed.

• ATCS-M60 and ATUC-IRDU compatibility: Both units draw from the same 7.4V two-cell Li-ion platform and use the same LI-240 form factor. The connector orientation, BMS communication lines, and physical dimensions are shared across both devices, so one part number covers both.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the ATCS-M60 transmitter body. The BMS reported state-of-charge correctly on the unit's indicator, and the protection circuit triggered cleanly at the low-voltage cutoff without causing an uncontrolled dropout.
• Transmitter RF output and voltage floor: The ATCS-M60 maintains full transmit power only above a specific cell voltage threshold. When the pack sags below roughly 6.8V under transmit draw, the unit reduces RF output before cutting off completely. Swap the battery before the indicator reaches the last segment — do not run it to zero.

Why the ATCS-M60 drops audio mid-performance on a near-full battery

A Li-ion pack that has been cycled heavily loses internal capacity while still reporting a partial charge. The ATCS-M60's fuel gauge reads voltage, not true capacity — so a degraded cell can show two bars and still sag under the transmitter's sustained RF draw. This voltage sag crosses the BMS protection threshold and triggers a cutoff that looks identical to a dead battery. If dropouts happen consistently at the same point in a session, the pack has degraded past its usable range and needs replacement.

Receiver loses lock on the ATCS-M60 transmitter after a battery swap

Swapping the battery mid-session without power-cycling the transmitter can leave the RF link in a broken handshake state. The receiver continues searching for the transmitter's last known signal parameters, but the transmitter reinitialises on fresh power and briefly shifts its output state. Power the transmitter off completely, seat the new LI-240, then power on and allow 5–10 seconds before checking receiver lock. If the receiver still shows no lock, press the transmitter's power button once to force a link re-broadcast.