Zoom Q4 Replacement Battery BT-02 3.7V 1050mAh

Zoom Q4 Handy Video Recorder — 3.7V Li-ion Replacement Battery (BT-02)

This 3.7V, 1050mAh lithium-ion cell replaces the OEM BT-02 battery in the Zoom Q4 Handy Video Recorder. It fits the Q4 and Q4-series units (including 247-9036) used for field audio and video capture. Dimensions are 43.30 × 31.30 × 7.10mm — match these before fitting if you are unsure of your unit revision.

• Q4 and Q4 Handy Video Recorder compatibility: Both models run the same 3.7V single-cell architecture with the BT-02 connector and contact layout. The BMS in each unit reads the same voltage thresholds, so one cell covers both variants without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Q4 hardware. The BMS accepted the cell without error flags, completed a full charge without thermal cutoff, and the recorder powered on normally at each stage of the discharge curve.
• First-cycle conditioning on the Q4: Charge this cell fully inside the Q4 body before your first recording session. The Q4's battery-remaining indicator calibrates its threshold map during the first in-body charge cycle — skipping this step can cause the indicator to report inaccurate levels until a full cycle is completed.

Q4 battery indicator dropping to zero before the cell is actually flat

The Q4 maps its battery-remaining display against a fixed voltage-threshold curve calibrated to the original BT-02's discharge profile. A replacement cell with a slightly different discharge curve can cause the indicator to hit zero while the cell still holds usable charge. This is a display mapping issue, not a cell fault. Run the recorder until it shuts down on its own, then charge fully in the body — one complete cycle usually brings the indicator back into step with actual capacity.

Q4 not recognising the replacement cell on first install

If the Q4 powers on but immediately displays a low-battery warning or shuts down after inserting a new cell, the BMS has not yet accepted the replacement. Remove the cell, reinsert it firmly, and connect the recorder to its charger before powering on. Allow a full charge cycle to complete from within the body. After that cycle, the unit should recognise the cell and resume normal operation at 3.7V nominal.