Sony FDR-AX40 Replacement Battery NP-FV50A 7.3V 2050mAh

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

This is a 7.3V, 2050mAh Li-ion replacement for the Sony NP-FV50A battery pack. It fits the FDR-AX40, FDR-AX45, FDR-AX60, HDR-CX625, and nine additional Sony camcorder models. Capacity figure is taken from the product specification — 14.97Wh.

• FDR-AX / HDR-CX platform fit: These models share the NP-FV50A form factor, InfoLITHIUM communication pins, and the same 7.3V nominal rail. The battery slot, latch geometry, and BMS handshake protocol are identical across the listed models, so one part number covers the full group.
• Bench tested on actual hardware: We ran this cell through the FDR-AX40 body and a Sony BC-QM1 charger. The BMS accepted the cell, the InfoLITHIUM percentage display initialised correctly after one full charge cycle, and thermal cutoff did not trigger during sustained 4K recording.
• First-use initialisation on InfoLITHIUM cameras: Charge this battery fully inside the camera body or an OEM-compatible Sony charger before your first shoot. Sony's InfoLITHIUM system maps remaining capacity against a learned discharge curve — skipping this step can cause the percentage indicator to read inaccurately from the outset.

Why the FDR-AX40 rejects a third-party cell on first install

Sony's InfoLITHIUM BMS sends a handshake query to the battery pack on every power-on. A new cell that has not yet completed a charge cycle from within a recognised charger may return an incomplete response — the camera then displays a battery warning or shuts down pre-emptively. This is not a defective cell. Place the battery in the camera or an OEM charger, run a full charge to 100%, then re-insert. One completed cycle is usually enough for the handshake to resolve.

Battery percentage jumping or freezing on the FDR-AX40 display

InfoLITHIUM percentage readings are voltage-threshold based, not coulomb-counted in real time. A replacement cell with a slightly different discharge curve can cause the indicator to skip steps — jumping from 80% to 50% with no warning, or holding a fixed percentage for an extended period. This does not mean the cell is faulty. Run two full charge-discharge cycles through the camera body and the indicator map recalibrates to the new cell's actual curve. If the display still jumps after three cycles, check that the battery contacts are clean and seated fully — a resistance gap at the connector distorts the voltage reading the BMS uses to calculate remaining charge.