About this replacement
Sony FDR-AX40 / FDR-AX45 Series — 7.3V Li-ion Replacement Battery (NP-FV100A)
This is a 7.3V, 3050mAh Li-ion replacement for the Sony NP-FV100A battery pack. It fits the FDR-AX40, FDR-AX45, FDR-AX60, HDR-CX625, and nine additional Sony camcorder models. Slot it into the same battery bay as the original — same connector, same form factor.
- FDR-AX / HDR-CX platform fit: These camcorder lines share the NP-FV series battery interface — same 7.3V rail, same three-pin connector, and the same BMS handshake protocol. A single cell covers the full range without any adapter or modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an FDR-AX40 body. The BMS accepted the cell on first insert, reported charge status correctly, and held voltage under sustained 4K recording load without triggering a low-voltage cutoff prematurely.
- First-use charge cycle on the FDR-AX40: Seat the battery in the camera body and run a full charge cycle through the camera itself before shooting. Sony's BMS maps the discharge curve during that first in-body charge — skipping it can cause the remaining-battery indicator to read inaccurately for the first few sessions.
Why the FDR-AX40 drains faster under 4K with image stabilisation active
4K recording on the FDR-AX40 runs the sensor, processor, and Balanced Optical SteadyShot (BOSS) stabilisation simultaneously. That combination pulls significantly more current than standard HD recording with stabilisation off. A cell at 3050mAh is rated at a steady draw — real-world 4K with BOSS active spikes current demand beyond that baseline. If the camera feels warm and the battery indicator drops faster than expected, stabilisation mode and recording resolution are the first variables to check.
Battery percentage jumping erratically on the FDR-AX40 display
This happens when the camera's indicator hasn't yet mapped the new cell's discharge curve. The Sony BMS uses voltage thresholds calibrated to the OEM cell — a replacement cell may discharge along a slightly different curve, causing the percentage to skip or stall at certain points. It typically self-corrects after two or three full charge-discharge cycles. Run the battery down to the auto-shutoff point and recharge fully each time — by the third cycle the indicator should track steadily.