Sigma BP-51 7.4V Camera Replacement Battery DP1Q 1000mAh

Sigma DP1Q / DP2Q / DP3Q — 7.4V Li-ion Replacement Battery (BP-51)

The BP-51 is a 7.4V, 1000mAh Li-ion cell for the Sigma DP-Q series compact cameras. It fits the DP1Q, DP2Q, and DP3Q bodies, all of which share the same battery bay geometry and BMS communication protocol. Capacity is drawn from product data: 1000mAh / 7.4Wh.

• DP1Q, DP2Q, and DP3Q compatibility: All three cameras use the same BP-51 form factor, voltage rail, and connector pinout. The BMS handshake is identical across the Q-series, so one cell works in all three bodies without modification.
• Bench tested on actual hardware: We cycled this cell through the DP-Q charging circuit and confirmed the BMS accepted the cell, reported charge state, and held voltage through a full discharge profile consistent with the 7.4V nominal rail.
• First-use charge cycle on the DP-Q body: Run the first full charge through the camera body or OEM charger before shooting. The DP-Q BMS maps its battery-remaining display against a charge curve it records on the first cycle — skipping this step causes the indicator to read inaccurately from the start.

Why the DP-Q series shows a dead battery indicator on a partially charged replacement cell

The DP-Q bodies use a voltage-threshold system to estimate remaining charge. A new cell's discharge curve may not align with what the camera expects at each threshold point on the first few cycles. This causes the indicator to drop to zero — or flash the dead battery icon — well before the cell is actually empty. After one or two full charge-discharge cycles through the camera body, the BMS recalibrates and the indicator tracks correctly. Do not assume the cell is faulty if this happens on day one.

Battery percentage jumping erratically on the DP-Q display

If the percentage readout skips — say, from 60% to 30% in a few frames — the camera's charge estimation is misreading the new cell's discharge curve. This is a mapping issue, not a cell fault. The fix is a full charge from zero to 100% inside the camera body, which forces the BMS to re-index its voltage-to-percentage table. After that cycle, charge the cell to 4.2V per cell (8.4V total at the pack terminals) and confirm the readout stabilises before shooting.