Sony NP-BY1 Action Cam Compatible Battery 3.7V 640mAh

Sony Action Cam Mini AZ1 / HDR-AZ1 Series — 3.7V Li-ion Replacement Battery (NP-BY1)

This is a 3.7V, 640mAh (2.37Wh) Li-ion cell built to the NP-BY1 specification. It fits the Sony Action Cam Mini AZ1, HDR-AZ1, HDR-AZ1/W, and HDR-AZ1VR. The cell matches the original's footprint exactly at 38.20 × 26.82 × 7.34mm, so it seats and locks without modification.

• AZ1 series compatibility: The HDR-AZ1 family shares a single battery bay spec — same voltage rail, same lock tab position, same BMS handshake protocol across all variants. One cell works across the full lineup listed above.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an HDR-AZ1 body. The BMS accepted the cell on first install, reported state-of-charge without error, and held the protection circuit cutoff at the correct low-voltage threshold.
• First-cycle initialisation on the AZ1: The AZ1's battery indicator can misread a new cell if you pull it mid-charge. Run the first charge to 100% uninterrupted — either in the camera body or the BC-BY1 charger — before shooting. This lets the BMS map the cell's discharge curve accurately from the start.

Why the AZ1 rejects a third-party cell on first install

Sony's AZ1 BMS runs a voltage-window check the moment a battery seats. If the cell arrives at the camera below roughly 3.0V — common after extended warehouse storage — the body flags it as unreadable and shows a blinking battery icon. This is not a compatibility fault. Place the cell in the BC-BY1 external charger first and bring it to full charge before inserting it into the camera. Once the BMS sees the cell enter from a known-good voltage, it accepts and tracks it normally on every subsequent cycle.

Battery percentage jumping erratically on the AZ1 display

The AZ1 maps remaining capacity using voltage thresholds calibrated to Sony's original NP-BY1 discharge curve. A new replacement cell — even a spec-matched one — can show percentage jumps of 20–30% between readings until the camera's BMS has logged one or two full charge-discharge cycles. The cause is a mismatch between the camera's expected voltage steps and the actual curve of the new cell. Run two full cycles from 100% charge to automatic shutoff and the indicator stabilises.