Sagem Alium 3.7V Replacement Battery 523855AR 1300mAh

Sagem Alium — 3.7V Li-ion Replacement Battery (523855AR)

This is a 3.7V, 1300mAh Li-ion cell for the Sagem Alium smartphone. It replaces OEM part 523855AR directly. The battery fits the Alium (model reference 253491226) and restores power to a device that no longer holds a charge.

• Alium and 253491226 compatibility: Both model references share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 523855AR footprint — 60.00 × 38.12 × 5.75mm — is consistent across both variants, so one cell covers the full run.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Sagem Alium unit. The BMS accepted the charge IC handshake without fault codes, and voltage held stable under combined screen and modem load without triggering the protection cutoff.
• Fuel gauge recalibration on first use: On first installation, disable fast charging if available and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts reading percentage from it — skipping this step causes erratic percentage readings in the first few days.

Sudden shutdown at 20–30% on the Sagem Alium

This happens when the cell voltage drops below the modem's or display's minimum operating threshold under load, even though the fuel gauge still reads a healthy percentage. The fuel gauge IC is still using the old cell's discharge curve as its reference — it reads voltage, not actual charge remaining. Under high-current draw from the radio stack or screen backlight, the new cell's voltage sags faster than the old curve predicts. One full discharge-charge cycle at standard rate recalibrates the coulomb counter and eliminates most unexpected cutoffs.

Phone won't power on after the replacement cell sat in storage

If the battery discharged below approximately 2.5V during storage, the BMS enters lockout mode to prevent cell damage — the phone shows nothing when you press power. Connect to a wall charger, not a PC port, and leave it for 15–20 minutes without attempting to power on. The charge IC needs to push a small trickle current into the cell to bring it above the BMS re-enable threshold, usually around 2.9–3.0V. Once the phone shows the charging indicator, a full charge cycle can proceed normally.