DJI MIC 2 Charging Case Replacement Battery 3.85V 450mAh

DJI MIC 2 Charging Case — 3.85V Li-Polymer Replacement Battery (W731834)

This is a 3.85V, 450mAh Li-Polymer battery for the DJI MIC 2 charging case. It replaces part number W731834 — the internal cell that keeps the case topped up and ready to recharge your MIC 2 transmitters and receiver on location. When this cell degrades, the case stops holding charge and your transmitters go into a shoot without a full top-up.

• MIC 2 Charging Case fit: The case uses a compact Li-Polymer cell running a 3.85V nominal rail to match the internal charge management circuit. W731834 is the only listed OEM part number for this unit — there is no cross-compatible variant from another DJI case that shares this footprint and BMS handshake.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a case unit. The BMS accepted the cell without fault codes, charge pass-through to the transmitter bays functioned normally, and the LED indicator sequence behaved as expected across the full state-of-charge range.
• Case storage between shoots: Do not leave the case fully depleted in a bag for weeks. Li-Polymer cells at near-zero charge self-discharge below the BMS recovery threshold faster than larger cells — a brief top-up charge before storage keeps the cell above 3.6V and prevents a locked-out BMS on your next job.

Why the MIC 2 case LED flashes but transmitters never reach full charge

A degraded case battery can hold enough charge to light the LEDs but not enough to push a full charge cycle into both transmitter bays simultaneously. The case BMS throttles output current when the cell voltage sags mid-cycle. You will see the transmitter indicator stall at two bars and stop climbing. Replacing the W731834 cell restores the full capacity needed to complete both charge cycles back-to-back.

Charging case showing full on the indicator but transmitters die early in a session

This is a cell-age problem, not a transmitter problem. A worn Li-Polymer cell reads near-full voltage under no load, so the LED indicator shows full — but voltage collapses as soon as current flows into the transmitter bays. The transmitters receive a partial charge and run out faster than expected in the field. Swap the case battery and confirm it holds above 3.85V under charge load before your next shoot.