Fujifilm NP-120 FinePix 603 Replacement Battery 3.7V 1800mAh

Fujifilm FinePix F10 / F11 / 603 Series — 3.7V Li-ion Replacement Battery (NP-120)

This is a 3.7V, 1800mAh Li-ion cell built to the NP-120 spec. It fits the Fujifilm FinePix 603, F10, F10 Zoom, F11, and compatible models in that line. Slide it into the same battery door, same connector orientation as the original.

• FinePix compact platform fit: The 603, F10, F10 Zoom, and F11 all share the NP-120 form factor — same 3.7V rail, same physical dimensions (53.00 × 35.30 × 11.00mm), and the same single-cell BMS communication line. One cell covers the group.
• Bench tested on actual hardware: We ran this cell through the FinePix body on our bench. The BMS accepted the cell on the first charge cycle via the OEM charger, reported charge state correctly, and held voltage above 3.5V through the bulk of the discharge curve before the low-battery indicator triggered.
• First charge cycle in the camera body: On the FinePix platform, charge the new cell inside the camera body using the OEM charger — not just a generic USB cradle — before your first shoot. Some FinePix BMS firmware maps battery-remaining percentage to the charge profile logged on that first cycle. Skipping this can cause the indicator to read inaccurately from day one.

Flash recycling slowing down mid-shoot on the FinePix F10 and F11

The F10 and F11 use the onboard flash heavily in auto mode, and flash capacitor recharge pulls a short but sharp current spike from the cell each cycle. As the cell discharges past the midpoint, internal resistance rises and that recharge spike causes a brief voltage sag. The camera throttles flash recycle speed to protect the BMS — you notice longer waits between shots. This is normal cell behaviour, not a fault. Keep the cell charged above 3.6V for full flash cadence.

Battery percentage jumping erratically on the FinePix display

The FinePix 603 and F-series bodies use a voltage-threshold system to estimate charge state — they do not have fuel-gauge ICs. A new cell has a slightly different discharge curve shape than a well-used original, so the camera misreads thresholds and the display jumps. Running one full charge-to-empty cycle through the camera body lets the body calibrate its threshold map to the new cell. After that cycle, the indicator stabilises. If it still jumps after two cycles, check the battery contacts for oxidation and clean with a dry cloth.