Wiko Sunset Li-ion Replacement Battery 3.7V 1200mAh

Wiko Sunset Series — 3.7V Li-ion Replacement Battery (SUNSET)

This is a 3.7V, 1200mAh Li-ion cell for the Wiko Sunset, Sunset neuwertig, and Sunset 2 smartphones. It replaces the original battery when the cell no longer holds a useful charge across a full day. Capacity is 4.44Wh, matching the stock specification.

• Sunset and Sunset 2 compatibility: Both handsets share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The BMS handshake uses the same thermistor line, so one cell fits either board without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Sunset platform. The BMS accepted the cell without error flags, and the charge IC hit the expected 4.2V cutoff on the first cycle.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge down to automatic shutoff, then charge to 100% uninterrupted. This gives the fuel gauge IC one full reference cycle against the new cell's actual discharge curve before it starts reporting percentages.

Why the Wiko Sunset reports wrong battery percentage after a cell swap

The fuel gauge IC on the Sunset stores a discharge curve model calibrated to the original cell. When a new cell goes in, that stored model no longer matches the actual voltage-to-capacity relationship of the replacement. The IC reads a voltage point on the curve and maps it to a percentage that was accurate for the old, degraded cell — not the fresh one. One full discharge-to-shutoff and uninterrupted charge cycle forces the IC to relearn the curve against the actual cell chemistry.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or display ramps current draw and the cell voltage drops sharply below the BMS cutoff threshold — typically around 3.0V under load. The fuel gauge may still show 20–30% because it hasn't recalibrated, but the actual cell voltage collapses faster than the IC predicts. Run one full recalibration cycle first. If shutdowns continue after calibration, check that the battery connector is fully seated — a loose pin increases internal resistance and accelerates the voltage sag under load.