Olympus BLH-1 Replacement Battery 7.4V 1050mAh Li-ion

Olympus E-M1 Mark II / OM-D — 7.4V Li-ion Replacement Battery (BLH-1)

This is a 7.4V, 1050mAh Li-ion cell built to the BLH-1 specification for the Olympus E-M1 Mark II and OM-D mirrorless camera bodies. It slots into the same battery compartment as the OEM unit and connects through the same contact array. Capacity is rated at 7.77Wh.

• E-M1 Mark II and OM-D compatibility: Both bodies run the same 7.4V battery rail and use the same BLH-1 form factor and contact layout. The BMS in each body reads cell voltage and temperature data through the same pin configuration, so one battery works across both platforms without modification.
• Bench tested on actual hardware: We cycled this cell through the E-M1 Mark II body under combined EVF, continuous autofocus, and 5-axis image stabilisation load. The BMS accepted the cell without rejection flags and held voltage above the camera's low-battery threshold through the full discharge cycle.
• First-use charge protocol for the E-M1 Mark II: Run the first full charge cycle through the camera body or the OEM BCH-1 charger rather than a third-party charger. The E-M1 Mark II BMS calibrates its battery-remaining display against the cell's charge profile during that first cycle — skipping it can cause the percentage indicator to read inaccurately for several subsequent charges.

Why the E-M1 Mark II battery percentage drops suddenly under sustained video recording

During video capture, the E-M1 Mark II draws simultaneously from the sensor, image processor, in-body stabilisation, and EVF. That combined load is significantly higher than the shot-count figure implies. Voltage sags faster under continuous draw than during stills shooting, which causes the BMS to interpret remaining capacity as lower than the resting voltage would suggest. The display percentage can drop several points in a short burst of recording and then stabilise once load eases. This is normal BMS behaviour under high sustained current draw — not a cell fault.

Battery percentage jumping erratically on the E-M1 Mark II display

The E-M1 Mark II maps its battery-remaining display to a voltage-threshold curve calibrated during the first charge cycle. A new replacement cell has a slightly different discharge curve than the depleted OEM cell it replaces, so the indicator can jump — for example, reading 80% then dropping to 65% between shots. The fix is one full charge-to-discharge cycle completed through the camera body. After that cycle, the BMS re-maps the display thresholds to the new cell's actual voltage curve and the readout stabilises. If jumping continues after two full cycles, check that the cell contacts are clean and seated fully against the body terminals.