AEG Fono 3 Compatible Battery BP-MPB16 3.7V 1200mAh

AEG Fono 3 — 3.7V Li-ion Replacement Battery (BP-MPB16)

This is a 3.7V, 1200mAh Li-ion cell built to replace the original BP-MPB16 battery in the AEG Fono 3 smartphone. It matches the OEM voltage, connector, and physical dimensions (53.18 × 34.00 × 6.80mm). Fit the battery when the original no longer holds charge or the phone shuts down unexpectedly.

• Fono 3 fit confirmation: The BP-MPB16 is specific to the AEG Fono 3 platform. The connector pinout and BMS handshake match the phone's charge IC, so the fuel gauge and thermal monitoring functions stay active after the swap.
• Bench tested on actual hardware: We cycled this cell through a full charge and discharge on test equipment. The BMS held cutoff voltage correctly at both ends and accepted the charge IC's CC/CV profile without dropping into fault mode.
• First-cycle calibration on the Fono 3: 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.

Why the Fono 3 reports wrong battery percentage after a cell swap

The fuel gauge IC in the Fono 3 stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour. The phone reads voltage and translates it to a percentage using stale data, so the number on screen drifts. One full discharge to auto-shutdown followed by a full charge resets the coulomb counter and aligns the gauge to the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under the load of the modem or screen backlight — a voltage cliff the fuel gauge IC did not predict. The phone's reported percentage still looks comfortable, but the actual cell voltage has already hit the BMS cutoff threshold. The fix is to let the phone run through two or three full discharge-charge cycles so the fuel gauge recalibrates. After calibration the percentage readout tracks the real voltage cliff and the phone shuts down near 5% instead of 25%.