Bea-fon S20 Replacement Battery 3.7V 1050mAh Li-ion

Bea-fon S20 / C200 / Classic Line C60 — 3.7V Li-ion Replacement Battery

This 3.7V 1050mAh Li-ion battery replaces the original cell in the Bea-fon S20, C200, and Classic Line C60 series phones. These are basic mobile phones built for calls and messaging, and this cell restores normal power when the original can no longer hold charge. Capacity is 1050mAh (3.89Wh) — matching the original specification.

• S20, C200, and C60 series compatibility: These models share the same battery bay dimensions, connector pin-out, and voltage rail at 3.7V nominal. The BMS handshake across this group is consistent, so one cell covers the full range without modification.
• Bench tested on actual hardware: We cycled this cell through full discharge and charge on the S20 platform. The BMS accepted the cell on first connection, protection circuits tripped correctly at low-voltage cutoff, and charge termination triggered at full capacity without overrun.
• Fuel gauge recalibration on first use: On first installation, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100% before use. This lets the fuel gauge IC map its internal charge curve against the new cell — without this step, percentage readings will be inaccurate from the start.

Sudden shutdown at 20–30% on the Bea-fon S20 after a cell swap

The S20 fuel gauge IC retains the discharge curve of the old, degraded cell in its coulomb counter memory. When a new cell is installed, the IC expects voltage to drop steeply at around 20–30% — the point where the old cell used to collapse — and signals shutdown even though the new cell still has usable capacity remaining. This is not a fault with the replacement cell. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% resets the coulomb counter and eliminates the premature cutoff.

Phone reports 100% immediately after installation without charging

If the S20 shows a full charge reading the moment a new cell is connected, the fuel gauge IC has not yet sampled the new cell's open-circuit voltage correctly. The IC is reading a cached reference, not the actual state of charge. Drain the phone completely until it shuts off on its own, then charge to 100% in a single session. After that cycle, the percentage display will track the actual cell state accurately.