Pentax D-LI8 Optio A10 Replacement Battery 3.7V 850mAh

Pentax Optio A10 / A20 / A30 / A40 Series — 3.7V Li-ion Replacement Battery (D-LI8)

This is a 3.7V 850mAh Li-ion cell built to the D-LI8 / D-Li85 specification used across the Pentax Optio A-series compact cameras. It fits the Optio A10, A20, A30, and A40 among others. Voltage and physical dimensions match OEM spec — 40.20 × 35.30 × 6.10mm.

• Optio A-series platform fit: The A10 through A40 share the same battery bay dimensions and 3.7V power rail. One BMS profile and connector pinout covers the entire run, so a single cell type works across all four bodies without modification.
• Bench tested on actual hardware: We ran the cell through full charge and discharge cycles on an Optio body. The BMS accepted the cell without fault codes, and protection circuits triggered correctly at low-voltage cutoff — no thermal events during the test sequence.
• First-use charge cycle on Optio bodies: Charge this cell once inside the camera body or OEM charger before heavy shooting. The Optio BMS maps its battery-remaining indicator against a discharge curve it builds on that first full cycle — skipping it causes inaccurate percentage readings from the start.

Optio A-series battery indicator stuck at full then dropping suddenly to empty

The Optio A-series uses a voltage-threshold system to estimate charge level. A new cell has a slightly different discharge curve than a worn OEM battery the camera has learned over time. The indicator reads the plateau voltage as full, then drops sharply when it hits the steeper end of the curve. One complete charge-discharge cycle recalibrates the threshold mapping. After that cycle, the readout tracks the actual cell state correctly.

Camera displaying no battery or refusing to power on with a new replacement cell

This happens when the cell voltage sits below the Optio's minimum startup threshold — typically under 3.4V — after sitting in storage. The camera interprets this as an absent or failed battery rather than a depleted one. Place the cell in the OEM charger for 15–20 minutes to raise it above the startup floor, then reinsert. If the camera still rejects it, check that the cell contacts are clean and fully seating against the body's battery bay terminals.