Bea-fon AL550 Replacement Battery SL550 3.7V 1200mAh

Bea-fon AL550 — 3.7V Li-Polymer Replacement Battery (SL550)

This is a 3.7V, 1200mAh lithium-polymer replacement battery for the Bea-fon AL550 mobile phone. It carries OEM part number SL550 and measures 54.20 × 34.30 × 7.90mm — same footprint as the original cell. If your AL550 no longer holds a charge or won't power on, this cell replaces the degraded original.

• AL550 fit: The AL550 uses a single-cell Li-Polymer pack at 3.7V nominal with a three-pad connector carrying positive, negative, and BMS data lines. This replacement matches that connector pinout and communicates with the phone's charge IC so the device recognises the battery on first boot.
• Bench tested on actual hardware: We cycled this cell through charge and load on the AL550 platform and confirmed the BMS handshake completed without fault codes. The charge IC accepted the pack and terminated correctly at 4.2V without thermal runaway flags.
• Fuel gauge recalibration after swap: After fitting this cell, disable any fast-charge mode and run one full discharge-to-charge cycle before normal use. This lets the AL550's fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes current into an uncalibrated pack.

Why the AL550 reports wrong battery percentage after a cell swap

The AL550 uses a fuel gauge IC that builds a discharge model from accumulated charge and load data. When you fit a new cell, that model still reflects the old cell's degraded curve. The phone reads state-of-charge against the wrong reference, so it shows 100% while the actual capacity is higher, or drops percentage faster than expected. One full discharge below 10% followed by a complete charge resets the coulomb counter and aligns the gauge to the new cell.

AL550 shuts down suddenly at 20–30% remaining

This happens when the cell cannot sustain its voltage under the load spike from the phone's modem or display. A depleted original cell sags below the BMS cutoff threshold during a call or screen-on burst even though the gauge still shows charge remaining. The replacement cell at full capacity holds voltage under those load spikes, so the cutoff should not trigger above single digits. If shutdowns persist after fitting this battery, run the fuel gauge recalibration cycle first — a miscalibrated gauge can trip a false low-voltage cutoff at the wrong percentage.