About this replacement
Canon C300 Mark I / EOS C100 Series — 7.4V Li-ion Replacement Battery (BP-975)
The BP-975 is a 7.4V, 6600mAh lithium-ion battery for Canon professional cinema cameras. It fits the C300 Mark I, EOS C100, EOS C100 Mark II, GL2, and 13 additional Canon models sharing the BP-975 form factor. Capacity is 48.84Wh — matched to the OEM specification.
- C300 Mark I and EOS C100 platform fit: These cameras share the BP-975 battery slot, connector pinout, and BMS communication protocol. The voltage rail and cell count are identical across the platform, so one battery services multiple bodies on a mixed kit.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a C300 Mark I body. The BMS handshake completed on first install, battery-remaining display updated correctly, and no authentication errors were logged during continuous recording.
- First-cycle initialisation on Canon cinema bodies: On initial install, run one full charge cycle through the OEM Canon charger or the camera body itself before heavy production use. Some Canon BMS firmware maps the battery-remaining percentage by completing a reference cycle — skipping this step can cause erratic percentage readouts on the first shoot day.
Why the C300 Mark I draws harder than the rated spec suggests
The C300 Mark I combines a Super 35 CMOS sensor, internal ND filter motor, dual recording paths, and continuous autofocus into a single power rail. Each system pulls current simultaneously during a take. That combined draw exceeds what a simple voltage and capacity rating predicts. A cell at 80% state of charge can show voltage sag under this combined load, which the BMS reads as a low-battery condition even when the displayed percentage still looks healthy.
Battery percentage jumping mid-shoot on the C300 Mark I
This happens when the camera's BMS is mapping percentage thresholds against a discharge curve it has not yet fully calibrated to the new cell. The OEM firmware uses voltage-to-percentage lookup tables tuned during a reference cycle. A new cell without that reference cycle completed will show erratic jumps — typically dropping 20–30% suddenly, then stabilising. Run one full charge-to-discharge cycle and let the camera reach a resting voltage of approximately 7.0V before recharging to reset the calibration baseline.