Leica Sofort Replacement Battery BP-DC17 3.7V 660mAh

Leica Sofort Series — 3.7V Li-ion Replacement Battery (BP-DC17)

This is a 3.7V, 660mAh lithium-ion cell replacing the OEM BP-DC17 in the Leica Sofort, Sofort Instant Film, and Sofort SP2 cameras. It powers the flash capacitor, autofocus motor, and exposure control circuits. When the original cell degrades, flash recycling slows and shot count drops — this replacement restores those systems to normal draw levels.

• Sofort, Sofort Instant Film, and Sofort SP2 compatibility: All three models share the BP-DC17 footprint, connector pinout, and BMS communication protocol. The same 3.7V voltage rail runs the flash charging circuit and the film advance motor across the entire Sofort line.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on Sofort body hardware and confirmed the BMS accepted the cell without rejection flags. Flash recycled normally and the indicator cleared on the first charge cycle completed inside the camera body.
• First-use charge protocol for Sofort bodies: Insert this cell and charge it fully inside the camera body before shooting. The Sofort BMS maps battery-remaining thresholds during the first in-body charge cycle — skipping this step causes the indicator to read inaccurately until the cycle completes.

Flash output dropping mid-shoot on a new BP-DC17 replacement

The Sofort flash capacitor pulls a high recharge current after every exposure. If the replacement cell has not completed a full in-body charge cycle, the BMS may apply a conservative current ceiling during that first session. This reduces the capacitor recharge rate and creates longer recycling delays between shots. After one complete charge cycle inside the camera body, the BMS lifts that ceiling and flash recycling returns to normal speed.

Battery percentage jumping erratically on the Sofort display

The Sofort maps its remaining-charge indicator to a fixed voltage-threshold table calibrated on the OEM cell's discharge curve. A new replacement cell discharges on a slightly different curve until the BMS has logged one full cycle. During that break-in session, the indicator reads across mismatched thresholds and jumps in uneven steps. Charge the cell to 100% inside the camera body, shoot until the low-battery warning appears, then charge fully again. After that single cycle, the indicator tracks normally at 4.2V full and steps down predictably.