Qumox SJ4000 Compatible Battery 3.7V 900mAh Li-ion

Qumox SJ4000 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion replacement battery for the Qumox SJ4000 action camera. It fits directly into the SJ4000 body and restores power to cameras where the original cell no longer holds a charge. At 32.77 x 29.16 x 10.89mm, it matches the original cell's physical footprint.

• SJ4000 platform fit: The SJ4000 uses a small single-cell Li-ion pack with a compact connector. This cell matches the voltage rail and physical dimensions the camera expects — no adapter or modification needed.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS responded normally through full charge and load draw, with no unexpected cutoff events during sustained recording load.
• First-use charge cycle: Insert the battery and charge it fully inside the camera body using the OEM cable before your first shoot. Some SJ4000 units require one complete in-body charge cycle before the battery-remaining indicator displays accurately on the LCD.

Why the SJ4000 shows a dead battery icon on a new, charged cell

The SJ4000's battery indicator maps percentage to voltage thresholds calibrated against the original cell's discharge curve. A new replacement cell may sit at a slightly different resting voltage after shipping, which the camera misreads as critically low or empty. This is not a fault with the cell — it is a threshold mismatch at first read. One full charge cycle inside the camera body resets the reference point and the indicator typically stabilises afterward.

Battery percentage jumping erratically on the SJ4000 display mid-recording

During sustained 1080p recording, the SJ4000 draws current from both the sensor and image processor simultaneously, causing brief voltage sag on the cell. If the indicator jumps — say, from 60% to 20% and back — the camera is misinterpreting momentary sag as a low-battery state. This is a display mapping issue, not cell failure. Let the battery complete two full charge-discharge cycles; the indicator reading typically settles to within a few percentage points of actual charge state by the third cycle. If it continues after three cycles, check that the cell contacts are clean and making firm contact at 3.7V nominal.