Sigma BP-21 SD14 Replacement Battery 7.4V 1500mAh

Sigma SD14 — 7.4V Li-ion Replacement Battery (BP-21)

This is a 7.4V, 1500mAh Li-ion replacement for the Sigma BP-21 battery. It fits the Sigma SD14 DSLR body directly, powering the imaging sensor, onboard processing, and all in-body electronics during shooting. Capacity matches OEM spec at 11.1Wh.

• SD14 platform fit: The SD14 uses a single-cell Li-ion pack at 7.4V nominal with a specific contact layout and BMS communication line. This replacement matches that voltage rail and connector geometry so the camera body reads the cell correctly.
• Bench tested on actual hardware: We cycled this cell through the SD14's charge and discharge sequence. The BMS handshake completed on first insertion, and the camera's battery indicator tracked discharge without false low-battery warnings during the test cycle.
• First-cycle initialisation on the SD14: Run a full charge through the OEM Sigma charger or direct in-body charging before your first shoot. The SD14's BMS calibrates its remaining-charge display against the new cell's discharge curve during that initial cycle — skipping it can cause the indicator to read inaccurately for the first few sessions.

Battery percentage jumping erratically on the SD14 display

The SD14 maps its battery indicator to a fixed voltage-threshold table calibrated for the original BP-21 discharge curve. A new replacement cell — even at full charge — discharges along a slightly different voltage slope until the BMS has logged one or two full cycles. During this break-in period, the indicator can jump forward or back by 10–20% between shots. Run two complete charge-to-discharge cycles and the BMS recalibrates its threshold mapping to the new cell. After that, the display tracks normally and stabilises around 3.6–3.7V per cell at the midpoint reading.

SD14 showing dead battery indicator on a cell that still has charge

The SD14 can throw a low-battery cutoff before the cell is genuinely depleted if the BMS hasn't completed its initialisation cycle with the new battery. This happens because the camera's protection circuit trips at a voltage threshold it expects from a worn OEM cell, not a fresh replacement. Remove the battery, reinsert it, and power on — the camera will often resume operation with charge remaining. To clear the fault properly, charge the replacement fully in-body once, which resets the BMS threshold reference to the new cell's resting voltage of approximately 8.4V at full charge.