About this replacement
Leagoo Lead 3 / Lead 3S — 3.8V Li-ion Replacement Battery (BT-450)
This is a 3.8V, 1400mAh Li-ion replacement battery for the Leagoo Lead 3 and Lead 3S smartphones. It uses OEM part number BT-450 and slots directly into either handset. Capacity is 1400mAh (5.32Wh), matching the original cell specification.
- Lead 3 and Lead 3S compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why a single BT-450 cell covers both. Voltage rail is 3.8V nominal on each board.
- Bench tested on actual hardware: We ran the BT-450 through a full charge-discharge cycle on a Lead 3 unit. The charge IC accepted the cell without fault, the BMS reported no protection events, and voltage held stable under screen-on and modem load.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the Lead 3's fuel gauge IC a clean reference curve for the new cell — skipping this step causes erratic percentage readings in the first few days.
Sudden shutdown at 20–30% on the Leagoo Lead 3
This is one of the most common complaints after a cell swap on the Lead 3. The fuel gauge IC is still calibrated to the discharge curve of the old, degraded cell — it does not match the new cell's voltage slope. When the modem transmits or the screen brightness peaks, current draw spikes and cell voltage drops momentarily below the BMS cutoff threshold, even though the reported percentage says 25%. The fix is a single uninterrupted full discharge-to-shutdown followed by a full charge. After that cycle, the coulomb counter resets against the actual cell curve and premature shutdowns stop.
Phone shows 100% but drops to 80% within minutes of unplugging
This happens because the fuel gauge IC logged the old cell's internal resistance as its baseline. A new cell has lower impedance, so the charge IC terminates early and the gauge overshoots to 100% before the cell is truly full. Once the device sits off-charge for a few minutes, open-circuit voltage settles and the gauge corrects downward sharply. Run one full discharge cycle to let the IC re-anchor its endpoint voltage — after recalibration, the reported percentage will track the actual state of charge accurately from approximately 4.2V full down to the 3.4V cutoff.