Rollei Action Cam 420 Replacement Battery 3.7V 1180mAh

Rollei Action Cam 420 — 3.7V Li-ion Replacement Battery (RL420B)

This is a 3.7V, 1180mAh Li-ion cell built to replace the original battery in the Rollei Action Cam 420 (also listed as Actioncam 420 and AC420). It matches the OEM voltage, physical dimensions (36.77 × 28.80 × 13.21mm), and connector orientation. When the original cell no longer holds charge through a full recording session, this is the direct swap.

• AC420 platform fit: The Action Cam 420, Actioncam 420, and AC420 all share the same battery bay and connector spec. The RL420B part number maps directly to this platform — voltage rail and physical form factor match without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS handshake and cutoff behaviour. The protection circuit tripped correctly at low-voltage threshold and accepted charge without error flags.
• First-cycle initialisation on the AC420: Run one full charge cycle inside the camera body or OEM charger before your first shoot. Some camera BMS systems need this initial charge cycle to begin reporting battery-remaining percentage accurately on the display.

Why the AC420 shows a dead battery indicator on a new replacement cell

The Action Cam 420 maps its battery indicator to a specific voltage-threshold curve calibrated against the original cell's discharge profile. A new replacement cell sitting at storage charge (typically 3.6–3.7V) can register as depleted if the camera has not yet completed a full charge cycle with it installed. The BMS has not established a baseline for the new cell's upper and lower voltage limits. One full charge from empty to 4.2V inside the camera body resets this mapping and brings the indicator in line with actual charge state.

Battery percentage jumping erratically on the AC420 display

This happens when the camera's voltage-to-percentage table does not yet match the discharge curve of the new cell. The indicator is reading real voltage, but translating it incorrectly. It is most noticeable in the middle percentage range — the display may skip from 60% to 20% without warning. Two full charge-discharge cycles through the camera body recalibrate the mapping; after that, the readout stabilises.