Leica BM8 Replacement Battery 3.7V 1600mAh BLI-312

Leica BM8 / M8 / M9 Series — 3.7V Li-ion Replacement Battery (BLI-312 / BP-SCL1)

This 3.7V, 1600mAh Li-ion cell replaces the OEM BLI-312 and BP-SCL1 batteries in the Leica BM8, M8, M8.2, and M9 film and digital rangefinder cameras. It powers every electronic function the body depends on — exposure metering, autofocus, flash, and shutter control. Capacity is 1600mAh (5.92Wh), matching original spec.

• BM8, M8, M8.2, and M9 compatibility: These bodies share the same battery bay dimensions, voltage rail, and BMS handshake protocol. One cell covers the whole rangefinder lineup that uses the BLI-312 or BP-SCL1 — no adaptor or modification needed.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes on an M8.2 body. The BMS accepted the cell without fault codes, and voltage stayed within the expected discharge curve across metering, flash cycling, and continuous shutter use.
• First-cycle initialisation on Leica rangefinder bodies: Charge the new cell inside the camera body or OEM charger before your first shoot. Some Leica BMS firmware requires an in-body charge cycle to map the new cell's discharge curve correctly — skipping this step can cause the battery-remaining indicator to read inaccurately until the first full cycle is completed.

Why the M9 battery indicator drops suddenly from 50% to empty

The M9 maps its battery-remaining display to a fixed voltage-threshold table calibrated against the OEM cell's discharge curve. A replacement cell with a slightly different discharge profile can appear to hold steady at mid-charge, then drop sharply as the voltage crosses a threshold the camera interprets as near-empty. This isn't a fault in the cell — it's the camera firmware reading a voltage point it associates with a depleted original battery. Running one full charge-to-discharge cycle inside the camera body allows the BMS to re-map its thresholds against the new cell's actual curve. After that cycle, the indicator tracks correctly.

Flash not fully recycling between shots on the BM8

The BM8's flash capacitor draws a sharp recharge current spike after each exposure. If the battery's internal resistance is elevated — either from age or from a cell that hasn't completed its first charge cycle — that current draw causes a voltage sag, and the capacitor takes longer to reach full charge voltage. The result is a longer recycle gap or a reduced-power flash on the next shot. Charge the replacement cell to 100% before a flash-heavy shoot, and confirm the cell voltage reads 4.1–4.2V on a multimeter before use.