About this replacement
DJI Osmo Action 3 / Action 4 / Action 5 Pro — 3.85V Li-ion Replacement Battery (BCX202)
This is a 3.85V, 1800mAh (6.93Wh) Li-ion replacement battery for the DJI Osmo Action 3, Osmo Action 4, and Osmo Action 5 Pro action cameras. It matches the BCX202 OEM part number and fits the same battery compartment across all three models. Voltage and cell format are consistent with the original specification.
- Osmo Action 3, 4, and 5 Pro compatibility: All three cameras use the same BCX202 cell format, voltage rail, and BMS handshake protocol. DJI carried the battery architecture across generations, so one cell works in all three bodies without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an Osmo Action 3 body. The BMS accepted the cell without error flags, and the battery-remaining indicator tracked normally across the discharge curve.
- First-cycle initialisation on Osmo Action cameras: On first install, charge the battery fully from inside the camera body using the OEM or a USB-C cable before your first shoot. Some DJI BMS builds require an in-body charge cycle to calibrate the percentage display to the new cell's discharge curve — skipping this step can cause the indicator to jump erratically early on.
Why the Osmo Action 3 battery drains faster under 4K stabilised recording
At 4K with RockSteady or HorizonSteady active, the Osmo Action 3 draws on the processor, gyro sensors, and image stabilisation pipeline simultaneously. That combined load pulls significantly more current from the cell than standard 1080p recording. A 1800mAh cell at 3.85V has a fixed energy budget — high-draw modes spend it faster. If drain feels unusually quick, check that stabilisation modes are only enabled when needed.
Battery percentage jumping erratically on a new replacement cell
This happens when the camera's BMS has not yet mapped the new cell's discharge curve to its percentage thresholds. The original BMS calibration was built around the aged state of your previous cell, not a fresh one. The fix is straightforward: charge the replacement to 100% from inside the camera body, then allow it to discharge through normal use without interruption. After one full cycle, the indicator stabilises — the cell's voltage steps align with the camera's display logic at each percentage bracket.