About this replacement
Sony FDR-AX40 / FDR-AX45 / HDR-CX625 Series — 7.3V Li-ion Replacement Battery (NP-FV100A)
This is a 7.3V, 2700mAh lithium-ion replacement for the Sony NP-FV100A battery pack. It fits the FDR-AX40, FDR-AX45, FDR-AX60, HDR-CX625, and more than nine additional Sony handycam models sharing the same battery bay. Capacity figures come from the product data — 19.71Wh total energy.
- FDR-AX / HDR-CX platform fit: These models share the NP-FV series battery rail — same 7.3V nominal, same physical connector, same BMS communication protocol. Sony standardised this pack across its AX and CX handycam lines, so one cell covers a wide model range without any hardware modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Sony FDR-AX40 body. The BMS handshake completed on first install, battery-remaining display initialised correctly, and the camera drew steady current through 4K recording without triggering an early cutoff.
- First-use charge cycle on the AX40: On initial install, run one full charge cycle through the camera body or Sony OEM charger before shooting. The FDR-AX40's BMS uses that first cycle to map the new cell's discharge curve — skipping it can cause the battery percentage indicator to read inaccurately for the first few uses.
Why the FDR-AX40 drains faster during 4K than HD recording
The FDR-AX40 runs its Exmor R CMOS sensor, Bionz X processor, and optical image stabilisation simultaneously during 4K capture. Combined draw from these systems is significantly higher than standard HD recording. The battery's 2700mAh capacity is the same physical ceiling either way — 4K mode simply pulls harder against it. Switching to 1080p when power is low is the fastest way to extend a remaining charge.
Battery percentage jumping or freezing on the FDR-AX40 display
This happens when the camera's BMS hasn't yet mapped the new cell's discharge curve to its internal voltage thresholds. The NP-FV100A discharge profile slopes differently to a partially aged original cell, so the indicator can read 80%, then jump to 50% without warning. Performing a full charge cycle — from 0V trigger to full charge — inside the camera body resets the calibration. After one complete cycle, the readout stabilises and tracks the actual cell voltage accurately at each threshold point.