About this replacement
Leagoo Alfa 5 — 3.8V Li-ion Replacement Battery (BT-501)
This is a 3.8V, 1900mAh Li-ion replacement battery for the Leagoo Alfa 5 smartphone. It matches the OEM BT-501 specification and fits the original battery compartment at 76.15 × 55.32 × 4.20mm. Swap it in when your original cell no longer holds charge through a normal day of calls and screen use.
- Alfa 5 fitment: The Alfa 5 uses a removable rear cover with a direct-contact battery bay. This cell matches the BT-501 connector tab placement and voltage rail so the phone's charge IC picks it up without manual pairing or firmware changes.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the bench. The BMS held cutoff cleanly at the low-voltage threshold and accepted a standard charge current without triggering thermal shutdown.
- Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after installation. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins. Skipping this step is the most common cause of erratic percentage readings in the first week.
Sudden shutdown at 20–30% on the Alfa 5 after a cell swap
This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under modem and screen load before the gauge registers low battery. The phone cuts power to protect the cell even though the display shows charge remaining. Run one full discharge to 0% and a full charge to 100% uninterrupted — the coulomb counter resets and the shutdowns stop.
Phone won't power on after the BT-501 sat in storage
Li-ion cells self-discharge in storage, and if the BT-501 dropped below approximately 2.5V per cell, the BMS enters lockout mode to prevent damage. Plugging in a charger at this point often shows no charging indicator at all. Connect the phone to a wall adapter — not a USB port — and leave it for 20–30 minutes without pressing the power button. The charge IC will trickle current into the cell until it clears the BMS lockout threshold, after which the phone boots normally.