About this replacement
Bea-fon SL250 — 3.7V Li-ion Replacement Battery (SL250)
This is a 3.7V, 1050mAh Li-ion cell for the Bea-fon SL250 mobile phone. It replaces the original battery when the cell has degraded, holds less charge, or no longer powers the device. Capacity figures are taken directly from the product specification — 3.89Wh total energy.
- SL250 platform fit: The SL250 uses a fixed 3.7V single-cell Li-ion configuration with a direct connector match. The BMS handshake on this platform is straightforward — no proprietary authentication chip, so the replacement cell communicates cleanly with the charge IC on the mainboard.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SL250 mainboard. The BMS accepted the cell without error flags, charge termination triggered correctly at 4.2V, and the fuel gauge IC updated its state-of-charge reading within the first full cycle.
- Fuel gauge recalibration on first use: On first installation, disable any fast-charge mode and run one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.
Why the SL250 reports wrong battery percentage after a cell swap
The SL250 uses a fuel gauge IC that builds its state-of-charge model against the original cell's discharge curve. When a new cell is installed, the IC is still referencing the old cell's data. Until it completes a full calibration cycle, percentage readings will be inaccurate — often appearing lower than actual charge. Run one full discharge down to auto-shutdown, then charge uninterrupted to 100% to reset the IC's reference curve.
Sudden shutdown at 20–30% on the replacement cell
This happens when the fuel gauge IC hasn't yet calibrated to the new cell and the reported percentage is ahead of actual cell voltage. Under screen or modem load, the cell voltage drops below the BMS cutoff threshold — typically around 3.0–3.2V — before the OS registers low battery. The phone shuts off to protect the cell. One full discharge-charge cycle resolves this by aligning the IC's coulomb counter to the new cell's actual capacity floor.