Bea-fon AL250 C140 Replacement Battery 3.7V 900mAh

Bea-fon AL250 / C140 Series — 3.7V Li-ion Replacement Battery (C140/C240)

This 3.7V 900mAh (3.33Wh) Li-ion cell replaces the original battery in the Bea-fon AL250 and a range of related models including the AL450, C70, and C140. It matches the OEM voltage and physical footprint at 53.00 × 34.00 × 4.30mm. Fits the connector and bay geometry on all listed Bea-fon models without modification.

• AL250 / C140 series compatibility: These models share the same battery bay dimensions, 3.7V supply rail, and C140/C240 connector format. The BMS handshake on each device expects the same charge termination voltage, so one cell covers the full listed range.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the AL250 platform. The BMS accepted the cell immediately, hit full termination voltage without fault flags, and held voltage under screen-on modem load without sagging below the low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: On first installation, disable any fast charging and run one complete discharge-to-charge cycle before normal use. The fuel gauge IC calibrates its coulomb counter against the new cell's discharge curve on that first pass — skipping it causes the percentage readout to drift for the first several cycles.

Sudden shutdown at 20–30% on the AL250 after a cell swap

A new cell has a slightly different internal resistance profile than the aged cell the fuel gauge IC was calibrated against. Under modem burst or backlight load, voltage drops faster than the gauge predicts, and the device hits the hardware cutoff before the displayed percentage reaches zero. The result is an abrupt shutdown while the screen still shows 20–30% remaining. One full discharge-charge cycle recalibrates the coulomb counter to the new cell curve, and the shutdowns stop. After the calibration cycle, the low-voltage cutoff typically realigns to trip at or below 3.4V under load.

Device will not power on after the replacement battery sat in storage

Li-ion cells ship at a partial state of charge and self-discharge in storage. If the cell dropped below approximately 2.5V per cell before installation, the BMS enters a lockout state and blocks normal charge current to prevent damage. The phone will show no charge indicator and will not respond to the power button. Connect it to a charger and leave it for 20–30 minutes without attempting to power it on — most Bea-fon charge ICs trickle current into a locked-out cell to recover it to 2.9V, at which point the BMS releases and normal charging resumes.