About this replacement
Sony DSLR-A100 Series — 7.4V Li-ion Replacement Battery (NP-FM55H)
This is a 7.4V, 1400mAh Li-ion replacement for the Sony NP-FM55H battery pack. It fits the Sony Alpha DSLR-A100, DSLR-A100K, DSLR-A100W, and DSLR-A100W/B. Dimensions are 55.76 × 38.53 × 20.40mm — same physical footprint as the OEM cell.
- A100 series compatibility: Every DSLR-A100 variant runs the same 7.4V power rail and uses the same NP-FM55H connector and BMS handshake. One cell covers the full lineup — no wiring differences between the K, W, and W/B suffixes.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the A100 body. The BMS accepted the cell without error flags, and the InfoLithium communication line reported charge state through the camera's battery indicator as expected.
- First-cycle initialisation on the A100: Charge this battery fully in the camera body or OEM charger before your first shoot. The A100's InfoLithium system maps battery-remaining percentage against a discharge curve — it needs one complete charge cycle to calibrate that display accurately on a new cell.
Flash capacitor recharge sag at low cell charge on the A100
The DSLR-A100's built-in flash pulls a sharp current spike to recharge the capacitor between shots. When the cell voltage drops toward the lower end of its discharge curve — around 6.8V — the camera body can't sustain that recharge current fast enough. Flash recycle time visibly lengthens, and in some cases the camera pauses before allowing the next shot. This is a voltage-sag behaviour, not a fault. Charge the battery before a flash-heavy session to keep cell voltage above 7.0V and maintain consistent recycle speed.
Battery percentage jumping erratically on the A100 display
The A100 uses Sony's InfoLithium system, which maps real-time voltage readings to a percentage scale calibrated to OEM cell discharge curves. A new third-party cell has a slightly different discharge profile, so the camera's mapping can misread state of charge — especially in the upper and lower thirds of the range. The percentage readout stabilises after one or two full charge-discharge cycles, once the BMS has logged the actual curve of the new cell. If the display still jumps after three cycles, check that the terminal voltage at full charge reads 8.2–8.4V with a multimeter.