About this replacement
Motorola Moto G04 / XT2421 — 3.91V Li-Polymer Replacement Battery (QF50)
This 3.91V, 4850mAh lithium-polymer cell is a direct swap for the Motorola Moto G04 and Moto G04s NFC 2024 (XT2421, XT2421-10). It replaces OEM part numbers QF50 and SB18D96852. Capacity degrades in original cells after 2–3 years of charge cycling — this cell restores full storage capacity to the device.
- Moto G04 and G04s NFC compatibility: The XT2421 platform uses a shared battery bay geometry (90.20 × 65.00 × 4.30mm) and the same fuel gauge IC across both the standard G04 and the G04s NFC 2024 variant. The BMS handshake and connector pinout are identical across these models, so one cell covers the full XT2421 line.
- Bench tested on actual hardware: We cycled this cell on an XT2421 unit and monitored the BMS across charge and discharge. The protection circuit responded correctly to both over-charge and over-discharge thresholds, and the fuel gauge IC accepted the new cell without triggering error flags after a full calibration cycle.
- First-cycle fast charge behaviour: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.
Why the Moto G04 reports wrong battery percentage after a cell swap
The G04's fuel gauge IC builds a discharge model from the previous cell's impedance and capacity curve. When a new cell goes in, that model is stale — the IC is reading voltage against the wrong reference. Until one full discharge-charge cycle completes, the reported percentage drifts significantly from actual state-of-charge. This is not a fault with the replacement cell. One uninterrupted cycle from 100% down to automatic shutoff, then back to 100%, resets the coulomb counter and aligns the gauge to the new cell.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff, not a software glitch. Under heavy load — modem transmit, display at full brightness, or active GPS — the cell voltage drops faster than the fuel gauge predicts. If the IC's curve is still calibrated to the degraded old cell, it underestimates how quickly voltage falls under load. The result is an abrupt shutdown while the display still shows 20–30% remaining. Run a full calibration cycle first, then check if the shutdown persists. If it continues after calibration, verify resting cell voltage is above 3.7V before reassembly.