BenQ E-40 Replacement Battery 3.7V 800mAh Li-ion

BenQ E-40 / S30 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 800mAh Li-ion cell that fits the BenQ E-40 and S30 compact digital cameras. It slots into the same battery compartment as the original and connects via the same contact layout. Capacity figure is taken directly from product data — 800mAh (2.96Wh).

• E-40 and S30 shared platform: Both cameras draw from the same 3.7V single-cell architecture and use the same physical footprint and contact arrangement. One cell covers both bodies — no adapter needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a controlled rig. The BMS responded correctly at both low-voltage cutoff and full-charge termination. Charge acceptance was consistent across repeated cycles.
• First-use charge cycle on these bodies: Run the first charge to full inside the camera body itself or via an OEM-compatible charger. The BenQ BMS uses that initial cycle to map the cell's discharge curve — skipping it can cause the battery indicator to read incorrectly from the start.

Battery percentage jumping erratically on the E-40 display

The E-40's battery gauge maps voltage thresholds to percentage steps. A new cell has a slightly different discharge curve than a worn original, so the camera's firmware can misread the state of charge early on. This shows up as the indicator jumping — say, from 80% straight to 40% — between shots. After one or two full charge-discharge cycles inside the body, the camera recalibrates to the new cell's curve and the display stabilises. If the jumping persists past three cycles, check that the charge terminated cleanly at 4.2V.

Flash not fully recycling between shots on a new cell

Flash recycling draws a sharp current spike to recharge the capacitor — far higher than any other load on these compact cameras. If the cell is at the low end of its charge state, voltage sag during that spike can cause the camera to slow recycle time or skip a flash entirely. This is not a fault with the cell; it is a consequence of shooting continuous flash near the bottom of the discharge curve. Keep the cell above 3.6V during flash-heavy sessions and recharge before extended shooting to avoid the sag.