Sony FDR-AX40 NP-FV50A Replacement Battery 7.3V 900mAh

Sony FDR-AX40 / FDR-AX45 Series — 7.3V Li-ion Replacement Battery (NP-FV50A)

This is a 7.3V, 900mAh (6.57Wh) lithium-ion battery built to the NP-FV50A spec. It fits the Sony FDR-AX40, FDR-AX45, FDR-AX60, HDR-CX625, and nine additional Sony camcorder models that share the same battery slot and voltage rail. Use it as a direct swap when the original cell no longer holds a usable charge.

• FDR-AX and HDR-CX platform fit: These models share the NP-FV50A form factor, connector pinout, and BMS handshake protocol. The 7.3V nominal rail is consistent across the range, so the same cell works in the body without modification.
• Bench tested on actual hardware: We cycled this cell in an FDR-AX40 body under continuous 4K recording load. The BMS accepted the cell without rejection, held voltage above the cutoff threshold throughout discharge, and reported charge status to the camera's indicator without fault.
• First-use charge cycle in the camera body: On first install, run one full charge cycle through the camera body or OEM charger before shooting. Sony's BMS maps the new cell's discharge curve during this cycle — skipping it can cause the battery-remaining indicator to display inaccurate percentages throughout the cell's life.

Why the FDR-AX40 battery indicator reads inaccurately with a new cell

Sony's camcorder fuel gauge maps battery percentage against a stored discharge curve from the previous cell. A new cell with a fresh capacity profile doesn't match that stored reference immediately. The result is percentage readings that jump, stall, or drop suddenly — especially in the first one to two cycles. After one or two full charge-discharge cycles inside the camera body, the BMS recalibrates against the new cell and the indicator stabilises.

Camera body shows "No Battery" or stops accepting the cell after install

This happens when the BMS authentication check doesn't complete on the first power-on — common with replacement cells that haven't been charged yet. Remove the battery, charge it fully in the OEM charger or via the camera's USB port, then reinsert. If the error persists, hold the camera's power button for ten seconds with the battery removed to reset the body's power state, then reinsert a fully charged cell. The camera should recognise it once voltage is above approximately 7.0V at the terminals.