Prestigio RoadRunner 300 Replacement Battery 40B 3.7V 700mAh

Prestigio RoadRunner 300 / LR-300 — 3.7V Li-ion Replacement Battery (40B)

This is a 3.7V, 700mAh Li-ion internal battery for the Prestigio RoadRunner 300 and LR-300 dashcams. It replaces the original part number 40B — the small cell mounted inside the camera body that keeps the unit alive during engine-off parking mode. When this cell degrades, parking mode fails first, then boot-on-ignition becomes unreliable.

• RoadRunner 300 and LR-300 fit: Both models share the same internal chassis, connector pinout, and BMS handshake protocol, which is why they run the same 40B cell. The cell dimensions are 40.00 × 31.10 × 5.90mm — tight tolerances inside the dashcam housing, so physical fit matters as much as voltage match.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the dashcam's own BMS. The protection circuit tripped correctly at the low-voltage cutoff threshold and accepted a full charge without thermal event or overcharge flag.
• First parking-mode calibration cycle: After installing a new internal cell, complete one full drive with the dashcam powered via the hardwire kit or USB before relying on parking mode. The dashcam's capacitor management needs one complete charge cycle against the new cell to calibrate parking mode duration accurately.

Why the RoadRunner 300 stops recording mid-session in parking mode

Parking mode on the RoadRunner 300 draws exclusively from the internal 40B cell — there is no vehicle power during this phase. A degraded cell loses usable capacity well before its rated voltage drops, so the dashcam's BMS cuts recording earlier than expected. The BMS monitors cell voltage continuously; once the cell sags below its cutoff threshold, it shuts down the camera to prevent deep discharge damage. A new 700mAh cell restores the full voltage headroom the BMS needs to sustain a complete parking-mode session.

Dashcam internal battery hot after a parking-mode session

The RoadRunner 300 sits inside an enclosed vehicle interior — temperatures climb quickly, especially in direct sun. Sustained parking-mode recording draws a continuous load from a small 700mAh cell inside a sealed housing with no airflow. If the cell feels hot to the touch after a session, that is a sign the original cell's internal resistance has climbed — higher resistance means more heat per milliamp drawn. Replace the cell and check that the dashcam's firmware is current, as newer firmware versions reduce parking-mode frame rate slightly to cut sustained draw on the internal battery.