Wiko Rainbow 3.7V 2000mAh Replacement Battery Li-ion

Wiko Rainbow (N350) — 3.7V Li-ion Replacement Battery

This is a 3.7V, 2000mAh Li-ion cell for the Wiko Rainbow smartphone, also listed as N350 and Rainbow Neongelb. It fits the original battery bay and connects to the same charge circuit. Use this when the original cell no longer holds adequate charge or fails to power the device on.

• Rainbow and N350 platform fit: These models share the same battery bay dimensions — 70.00 × 59.90 × 4.40mm — and the same 3.7V single-cell charge rail. The connector pinout and BMS handshake match across Rainbow, N350, Rainbow Neongelb, and M172 variants.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Rainbow platform. The BMS communicated correctly with the charge IC, accepted a full 3.7V charge cycle, and triggered protection cutoff at the expected low-voltage threshold without error flags.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing early erratic percentage readings.

Sudden shutdown at 20–30% on the Wiko Rainbow after a cell swap

The Rainbow's fuel gauge IC builds a discharge model from the original cell over time. When a new cell goes in, that model no longer matches the actual discharge curve of the replacement. The phone's software still predicts voltage drop using the old curve, so it underestimates how fast voltage falls under modem or screen load. The result is a hard shutdown well above 0% — typically between 20–30% — because the cell voltage drops below the protection threshold before the OS expects it. One full uninterrupted discharge-to-charge cycle forces the coulomb counter to recalibrate against the new cell.

Device won't power on after sitting in storage with low charge

If the battery discharged below roughly 2.5V during storage, the BMS enters lockout mode to prevent cell damage — the phone will show no response at all, including no charge indicator on the screen. Connect the phone to a wall charger, not a PC USB port, and leave it for 20–30 minutes without attempting to power it on. The charge IC needs to trickle current into the cell to bring it above the BMS re-enable threshold, typically around 2.9V, before normal charging and startup can resume.