Wiko Summer Li-ion Replacement Battery 3.7V 850mAh

Wiko Summer / Soap — 3.7V Li-ion Replacement Battery (SOAP)

This 3.7V 850mAh Li-ion cell replaces the original battery in the Wiko Summer and Wiko Soap smartphones. It fits both models because they share the same battery bay dimensions and connector pinout. Swap it in when the original cell no longer holds a charge or the phone refuses to power on.

• Summer and Soap compatibility: Both handsets run the same 3.7V battery rail with an identical physical footprint — 53.10 × 38.50 × 4.50mm — and share the same connector locking tab orientation. The BMS on each phone accepts the same charge termination voltage, so one cell covers both.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the bench. The BMS accepted the cell without error flags, charge termination fired correctly at 4.2V, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if your charger supports it and run one complete discharge down to auto-shutdown, then charge to 100% uninterrupted. The Wiko fuel gauge IC needs a full reference cycle against the new cell's discharge curve before its percentage readings stabilise.

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

The fuel gauge IC on the Wiko Summer stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour — the IC reads voltage and maps it to the wrong state-of-charge percentage. This causes the indicator to jump, stall, or report full charge well before the cell is actually full. One complete discharge-to-shutdown followed by an uninterrupted charge to 4.2V resets the coulomb counter reference and aligns the gauge to the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — modem transmit bursts and screen-on draw pull enough current to cause a brief voltage sag below the BMS cutoff threshold, even though the gauge still shows charge remaining. A fresh Li-ion cell with an uncalibrated fuel gauge makes this worse because the IC doesn't know the real remaining capacity at that voltage point. Run the phone through two full reference cycles — discharge to shutdown, charge to 100% — and the gauge IC will learn where the actual voltage cliff sits. After calibration, shutdowns at 20–30% typically stop.