Wiko WAX L5503AE Replacement Battery 3.7V 2000mAh

Wiko WAX / Rainbow 4G — 3.7V Li-ion Replacement Battery (WAX, L5503AE)

This is a 3.7V 2000mAh (7.4Wh) Li-ion replacement battery for the Wiko WAX and Rainbow 4G smartphones. It uses OEM part references WAX and L5503AE. The cell matches the original voltage rail and physical footprint — 70.05 × 59.95 × 4.31mm — so it seats correctly in both devices.

• WAX and Rainbow 4G compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V power rail. The BMS handshake protocol is identical across the two platforms, so one cell covers both without modification.
• Bench tested on actual hardware: We cycled this cell through charge and full discharge on a WAX unit. The BMS accepted the charge profile on the first cycle and held voltage above 3.5V through the mid-discharge range without tripping overcurrent protection.
• 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 map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first day.

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

The WAX fuel gauge IC stores discharge curve data from the previous cell. When a new cell with slightly different internal resistance is installed, the IC misreads remaining capacity. Under peak load — mobile data, screen-on, GPS active simultaneously — voltage drops faster than the IC predicts. The phone interprets this voltage cliff as a dead cell and shuts down, even though the percentage counter still reads 20–30%. One full discharge to auto-off followed by an uninterrupted charge to 100% forces the coulomb counter to reset against the new cell's actual curve.

WAX not powering on after the replacement battery sat in storage

Li-ion cells self-discharge during storage. If the cell voltage drops below approximately 2.5V per cell, the BMS triggers a lockout to prevent damage from deep discharge. The phone will show no response — no boot screen, no charge indicator — even when plugged in. Connect the phone to a wall charger rather than a USB port, leave it for 20–30 minutes without pressing the power button, and the charge IC will trickle current into the cell until the BMS releases the lockout. Attempt a power-on only after the battery icon appears on screen.