About this replacement
Wiko Y80 / W-V720 — 3.85V Li-Polymer Replacement Battery (386768)
This is a 3.85V, 3800mAh Li-Polymer cell for the Wiko Y80 and W-V720 smartphones. It replaces OEM part 386768 when the original battery no longer holds a charge. Dimensions are 86.90 × 66.45 × 3.72mm — confirm fit before installation if the rear housing has been replaced.
- Y80 and W-V720 platform: Both models share the same battery bay dimensions, voltage rail, and connector pinout, which is why they use the same 386768 cell. The BMS communicates charge state over the same two-wire interface on each variant.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Y80 platform. The BMS accepted the new cell without fault codes, and the charge IC reached full termination voltage at 4.35V as expected.
- Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes higher current into an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
A new Li-Polymer cell has a steeper voltage cliff than a worn cell at the same state of charge. The phone's fuel gauge IC is still reading from the old discharge curve stored in firmware, so it reports 25% when the cell voltage has already dropped to near the cutoff threshold under modem or screen load. The BMS trips the cutoff to protect the cell — the phone goes dark mid-use. One full discharge-charge cycle at standard rate lets the coulomb counter recalibrate and shifts the reported percentage back into sync with actual cell voltage.
Phone warm near the battery during the first few charge cycles
A fresh Li-Polymer cell has higher internal impedance than a broken-in cell. During the first few charge cycles, the charge IC pushes current into that higher impedance, and the resulting resistive heating is noticeable through the back cover. This is not a fault — impedance drops after three to five cycles and the warmth goes with it. If the phone stays hot past the fifth full cycle, check that the charge IC is terminating correctly at 4.35V and not entering a continuous top-up loop.