About this replacement
Nokia G10 / G20 Series — 3.85V Li-Polymer Replacement Battery (WT340)
This 3.85V, 4850mAh Li-Polymer cell replaces the original WT340 battery in Nokia G10 and G20 smartphones. It fits models including TA-1338 and TA-1344. Use the OEM part number WT340 to confirm your handset takes this cell before ordering.
- G10 and G20 platform compatibility: The G10 and G20 share the same battery bay dimensions, connector pinout, and BMS handshake protocol — Nokia standardised the WT340 cell across both lines. The 86.90 × 64.50 × 4.70mm footprint fits either chassis without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a G20 unit and monitored BMS communication throughout. The protection circuit held charge termination at the correct voltage and flagged overcurrent cleanly — no false trips during modem-heavy loads.
- 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 state. Skipping this step is the leading cause of erratic percentage readings post-swap.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff failure. The Nokia G10's processor, modem, and display pull current simultaneously under load, and if the cell cannot sustain voltage above the BMS cutoff threshold, the phone shuts off even though the fuel gauge still reads charge remaining. A new cell that has not completed a calibration cycle will trigger this because the coulomb counter is still referencing the old cell's discharge curve. Run one full discharge to 1–2% without fast charging, then charge to 100% without interruption. After that cycle, the fuel gauge IC recalibrates and the shutdowns typically stop.
Phone reports wrong battery percentage after cell swap
The G10's fuel gauge IC stores discharge curve data from the original cell in firmware. When a new cell goes in, the IC compares incoming voltage against that old curve — so the percentage shown can be 15–25% off in either direction. This is not a fault with the replacement cell. One complete uninterrupted discharge-charge cycle forces the coulomb counter to relearn the new cell's capacity endpoints. After that cycle, reported percentage should track actual charge state within a few percent across the full range.