Leaf AFi-II 7 Replacement Battery 7.4V 1850mAh Li-ion

Leaf AFi-II 7 / Aptus Series — 7.4V Li-ion Replacement Battery

This 7.4V, 1850mAh Li-ion battery fits the Leaf AFi-II 7 and Aptus medium format digital backs, including the Aptus 22, Aptus 65, and Aptus 75. It powers the imaging sensor, onboard processor, and operational functions of these high-resolution capture systems. No OEM part number is published by Leaf for this cell, but the voltage, capacity, and form factor match the original specification.

• AFi-II 7 and Aptus platform fit: These backs share a common battery bay and voltage rail at 7.4V nominal. The cell contacts and physical envelope — 70.60 × 38.20 × 20.60mm — are consistent across the AFi-II 7, Aptus 22, Aptus 65, and Aptus 75, which is why one cell covers this range.
• Bench tested on actual hardware: We ran full charge and discharge cycles across the rated capacity. The BMS responded correctly to charge termination at 8.4V and held cutoff thresholds at the low-voltage floor without tripping early under steady sensor draw.
• First-cycle charge in the OEM charger or camera body: Leaf digital backs can map battery-remaining display incorrectly if the first charge is done outside the body. Seat the new cell in the back and run one full charge cycle through the body or OEM charger before shooting — this allows the BMS to calibrate the discharge curve for accurate percentage readout.

Why the Aptus back shows a dead-battery indicator on a partially charged replacement cell

Leaf's battery indicator maps percentage to voltage thresholds calibrated against the original cell's discharge curve. A new replacement cell with a slightly different internal resistance will present a different voltage at the same state of charge. The back reads that voltage offset as a lower — sometimes critically low — charge level, triggering the dead-battery warning prematurely. One full charge cycle through the camera body resets the mapping and clears the false indicator.

Battery percentage jumping erratically during a shoot

Erratic percentage readings on a Leaf back usually come from the indicator firmware interpolating voltage against an outdated internal reference. When a new cell's discharge curve doesn't match the stored profile, the percentage can jump — say, from 60% to 30% — without any corresponding actual capacity drop. This is a display calibration issue, not a cell fault. Charge the battery fully via the body once, then discharge it completely through normal shooting, and repeat once more to let the back build an accurate reference map.