About this replacement
Olympus E-M5 / OM-D / E-M1 II — 7.6V Li-ion Replacement Battery (BLN-1)
This 7.6V 1050mAh Li-ion cell replaces the Olympus BLN-1 battery in the E-M5, OM-D, and E-M1 II mirrorless cameras. It slots into the battery compartment using the same form factor and connector as the original. Voltage and capacity match OEM spec — 7.6V at 1050mAh (7.98Wh).
- E-M5, OM-D, and E-M1 II compatibility: These bodies share the BLN-1 footprint, contact layout, and 7.6V power rail. The BMS handshake across all three uses the same authentication sequence, so one cell covers the full lineup without modification.
- Bench tested on actual hardware: We ran this cell through the E-M5 body, cycling through image capture, continuous AF, and in-body stabilisation draw. The BMS accepted the cell without tripping low-voltage cutoff and held a stable discharge curve across the full capacity range.
- First-cycle initialisation on Olympus bodies: Some Olympus mirrorless bodies require an initial charge completed inside the camera body — not just in an external charger — before the battery-remaining indicator calibrates correctly. Run one full charge cycle via the body on first use.
Why the E-M5 battery percentage jumps erratically with a new cell
The E-M5 maps its battery indicator against the original BLN-1 discharge curve. A new replacement cell may sit at a slightly different voltage at each charge state, so the camera's threshold logic reads it as a different percentage than actual capacity. This typically resolves after one or two full charge-discharge cycles as the BMS learns the cell's real curve. If the indicator still jumps after two cycles, run a full charge inside the camera body rather than in an external charger — the body calibration routine is more thorough than the external charger cycle.
Dead battery indicator showing on a cell that isn't empty
If the E-M5 displays the dead battery icon and shuts down immediately after inserting the replacement, the camera BMS has not yet accepted the new cell. This is an authentication check, not a fault with the cell itself. Remove the battery, reinsert it, and power the camera on once — if it still rejects, place the cell in the camera and charge via USB until the indicator shows at least one bar, then power on. Voltage at the cell terminals should read between 7.4V and 8.4V on a multimeter to confirm the cell itself is not at fault.