DJI MIC Replacement Battery BJX211 3.85V 300mAh Li-Polymer

DJI Mic Wireless Microphone Transmitter — 3.85V Li-Polymer Replacement Battery (BJX211)

This is a 3.85V, 300mAh Li-Polymer battery for the DJI Mic wireless microphone transmitter (BJX211). It fits the compact transmitter body used in DJI's wireless audio system for camera and drone recording. Swap it in when the original cell no longer holds charge or the transmitter shuts down mid-session.

• DJI Mic transmitter fit: The BJX211 cell is the only Li-Polymer size that fits the DJI Mic transmitter housing. The connector pinout and BMS handshake are specific to this unit — the transmitter will not power on if the voltage rail or cell ID doesn't match what the onboard protection circuit expects.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the DJI Mic transmitter. The BMS accepted the cell without fault flags, protection cut-off triggered correctly at low voltage, and charge termination registered cleanly on the DJI Mic charging case.
• Transmitter charging case compatibility: Always seat the transmitter fully into the DJI Mic charging case after fitting a new cell. A partial connection to the case contacts leaves the battery unprotected from over-discharge — the transmitter has no separate deep-discharge guard outside the case charging circuit.

Why the DJI Mic transmitter cuts out mid-recording on an aging battery

The DJI Mic transmitter draws a sustained current spike every time the RF module transmits. As the Li-Polymer cell ages, internal resistance rises. Under that transmit load, voltage briefly drops below the BMS cutoff threshold — roughly 3.0V — and the transmitter shuts down even if the indicator still showed charge. This is a cell-condition issue, not a pairing or range problem. Replacing the BJX211 cell restores the voltage headroom the RF module needs to sustain transmission without tripping the protection circuit.

Transmitter shows "charging" but never reaches full in the case

If the DJI Mic transmitter sits in the charging case for hours but the indicator stays at partial charge, the replacement cell may have entered deep-discharge protection during storage. The BMS locks charge acceptance when cell voltage drops below approximately 2.5V. Remove the transmitter from the case, hold the power button for 10 seconds to attempt a BMS wake, then re-seat it. If the case then shows a rising charge indicator, the cell is recovering — allow a full uninterrupted charge cycle before use.