About this replacement
Nokia G21 — 3.85V Li-Polymer Replacement Battery (WT341)
This is a 3.85V, 4900mAh Li-Polymer replacement battery for the Nokia G21 and G21 2022 smartphones. It replaces the original WT341 cell when capacity has degraded and the phone no longer holds a useful charge. Fit is direct — same footprint at 89.40 × 64.70 × 4.70mm.
- G21 and G21 2022 fitment: Both model years use the same WT341 cell spec — identical connector pinout, voltage rail at 3.85V nominal, and the same BMS handshake with the phone's charge IC. One replacement covers both variants.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the G21 platform. The BMS accepted the charge IC handshake without error. Voltage under screen-on and modem load held stable across the full discharge curve.
- First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before any high-current fast charge session pushes current into an uncalibrated cell — preventing erratic percentage readings from the first day.
Sudden shutdown at 20–30% on the Nokia G21 after a cell swap
This is a voltage cliff issue, not a defective cell. A fresh Li-Polymer cell has a discharge curve the phone's fuel gauge IC has never seen. When the modem or screen draws a current spike, the cell's instantaneous voltage drops below the shutdown threshold even though the coulomb counter still shows capacity remaining. The fuel gauge IC was calibrated against the worn original cell — it does not yet know where the new cell's real floor sits. One complete discharge cycle down to automatic shutdown, followed by a full charge, recalibrates the IC against the new curve and eliminates premature cutoff.
USB fast charge not activating after replacing the WT341
The Nokia G21's charge IC negotiates fast charge protocol on the first handshake after boot. If the new battery's BMS presents a state-of-charge the IC treats as out of range, it falls back to standard 5V charging and stays there. Power the phone off completely, connect the charger, then power on — this forces a fresh protocol negotiation. If fast charge still does not activate, let the cell reach at least 15% via standard charge first, then reconnect the charger to trigger renegotiation at a valid SOC.