About this replacement
Wiko Rainbow Up — 3.8V Li-Polymer Replacement Battery (TLP15F18)
This 3.8V, 2500mAh Li-Polymer cell replaces the original TLP15F18 / TLP15G07 battery in the Wiko Rainbow Up and Rainbow Up 4G Dual SIM LTE. The battery measures 75.85 × 59.30 × 4.00mm and fits the standard battery bay with the original connector. Use the capacity figure from this listing — 2500mAh (9.5Wh) — as your reference.
- Rainbow Up and Rainbow Up 4G Dual SIM LTE fitment: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol, so one cell covers both. The 4G LTE model draws heavier current during simultaneous dual-SIM data sessions — this cell handles that load without triggering cutoff.
- Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the Rainbow Up mainboard. The BMS handshake completed correctly, charge IC accepted the cell without error codes, and voltage held steady under combined screen and modem load.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-charge cycle at standard current. The fuel gauge IC calibrates against the new cell's discharge curve on that first cycle — skipping it can cause the OS to report inaccurate percentages for days afterward.
Sudden shutdown at 20–30% on the Wiko Rainbow Up
This is a voltage cliff, not a capacity problem. When the cell's internal resistance rises with age, voltage drops sharply under the combined load of the modem radio and display — even though the fuel gauge still reads 20–30%. The BMS cuts the circuit before the OS can write a shutdown log, so the phone just goes dark. A fresh cell with lower internal resistance holds voltage above the BMS cutoff threshold under that same load. After fitting the replacement, let the fuel gauge run one full cycle to remap the discharge curve against the new cell.
Phone won't power on after the replacement battery sat in storage
Li-Polymer cells self-discharge in storage, and if the cell drops below roughly 2.5V the BMS latches into lockout to prevent damage. Pressing the power button does nothing because the protection circuit has cut the output rail entirely. Connect the phone to a wall charger — not a PC USB port — and leave it for 15–20 minutes without pressing any buttons. The charge IC trickle-charges the cell back above the BMS recovery threshold, typically around 2.8–3.0V, at which point the BMS re-initialises and the phone will boot normally.