Olympus BLS-5 Replacement Battery 7.4V 1000mAh Li-ion

Olympus OM-D E-M10 / E-PL Series — 7.4V Li-ion Replacement Battery (BLS-5)

This is a 7.4V, 1000mAh (7.4Wh) Li-ion cell built to the BLS-5 spec. It fits the Olympus OM-D E-M10 mirrorless camera along with the E-PL5, E-PL6, and E-PL7, plus additional E-PL and E-PM body variants. It slides into the same compartment as the factory cell and uses the same contact layout.

• OM-D and E-PL platform fit: These bodies share the BLS-5 form factor, connector pinout, and BMS communication protocol across the range. One cell covers the entire group because Olympus standardised the battery slot across mirrorless and PEN bodies from this generation.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an E-M10 body. The BMS accepted the cell without error flags, and the protection circuit engaged correctly at the low-voltage cutoff threshold.
• First-cycle conditioning on the E-M10: Insert the cell and charge it fully through the camera body — not an aftermarket charger — before the first shoot. The E-M10's BMS maps its battery-remaining display to a discharge curve learned during that first in-body charge cycle. Skipping this step produces inaccurate percentage readings throughout the cell's life.

Battery percentage jumping erratically on the E-M10 display

The E-M10 uses a voltage-threshold model to estimate remaining charge. A new cell has a slightly different discharge curve than the factory cell the BMS was originally calibrated against. This causes the indicator to jump — for example, from 60% to 30% in a few frames — because the voltage is crossing thresholds at different points than expected. Run the cell down fully until the body shuts off, then charge it to 100% in-body without interruption. After one complete cycle, the BMS recalibrates and the percentage display stabilises.

Flash not fully recycling between shots on a fresh cell

The built-in flash on the E-M10 pulls a sharp current spike each time its capacitor recharges. At lower state-of-charge — typically below 3.6V per cell — internal resistance rises enough that the capacitor cannot recharge fully before the next frame. The result is visibly dimmer flash output or a longer wait between shots than the camera spec suggests. This is not a defective cell — it is the BMS protecting against voltage sag. Keep the cell above 50% charge during flash-heavy shooting to stay above the sag threshold.