Sigma BP-31 DP1 Replacement Battery 3.7V 1230mAh

Sigma DP1 / DP2 / DP2s — 3.7V Li-ion Replacement Battery (BP-31)

The BP-31 is a 3.7V, 1230mAh lithium-ion cell that powers the Sigma DP1, DP2, and DP2s compact cameras. These three bodies share the same battery bay dimensions and connector, so one cell covers the full DP1/DP2 lineup. Voltage and physical footprint match the OEM spec exactly at 38.32 × 38.11 × 9.41mm.

• DP1, DP2, and DP2s compatibility: All three bodies run the same 3.7V rail and use an identical battery bay with the same contact layout and BMS handshake protocol. A cell that works in the DP1 will seat and communicate correctly in the DP2s without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the DP2 body. The BMS accepted the cell on first install, reported a stable state-of-charge reading, and held the voltage curve within expected bounds across the full discharge cycle.
• First-cycle initialisation on the DP1/DP2 body: Charge this cell through the camera body or OEM charger before your first full shoot. The Sigma BMS maps remaining capacity against the cell's discharge curve during that initial cycle — skipping it can cause the battery indicator to read inaccurately until calibration completes.

Why the DP1's Foveon sensor draw accelerates cell depletion during burst capture

The Foveon X3 sensor captures full colour data at every pixel site rather than interpolating from a Bayer array. That process puts a heavier sustained load on the image processor during burst shooting compared with a conventional sensor of similar resolution. The increased processor draw pulls more current from the cell in short windows, which can push the BMS closer to its low-voltage cutoff faster than the shot count alone would suggest. Shooting in single-frame mode and letting the buffer clear between captures reduces peak current draw and keeps the cell working inside its rated discharge curve.

Battery percentage jumping erratically on the DP2 display

This happens when the camera's fuel gauge hasn't mapped the replacement cell's discharge curve yet. The OEM firmware uses voltage thresholds calibrated against the original BP-31 discharge profile — a new cell with a slightly different curve reads those thresholds inconsistently until one full charge cycle is logged. Run the cell down to automatic shutoff via normal shooting, then charge it fully without interruption. After that cycle, the percentage indicator should track smoothly and stabilise near 4.1V at full charge.