About this replacement
Leagoo M8 / M5 Max — 3.8V Li-ion Replacement Battery (BT-572P)
This is a 3.8V, 2000mAh Li-ion replacement battery for the Leagoo M8 and M5 Max smartphones. It carries OEM part number BT-572P and fits both models due to shared cell dimensions of 82.50 × 69.10 × 4.75mm and the same voltage rail. Capacity is rated at 7.6Wh.
- M8 and M5 Max cross-compatibility: Both phones use the same physical cell format, voltage rail, and BMS connector pinout. The BT-572P fits either model without modification. Verify the part number on your existing cell before ordering if you are unsure which model you have.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the M8 platform. The BMS handshake completed on the first cycle, the charge IC accepted current without interruption, and voltage held stable under simultaneous screen and modem load.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge-to-charge cycle before normal use. This lets the fuel gauge IC map the new cell's discharge curve. Without this step, the coulomb counter remains calibrated to the old cell and will report inaccurate percentages.
Why the M8 reports wrong battery percentage after a cell swap
The M8 uses a fuel gauge IC that builds its percentage model from the discharge curve of whichever cell is installed. When you fit a new cell, the IC still holds calibration data from the degraded original. Until you complete a full discharge and charge cycle, the reported percentage can read 10–20% higher or lower than actual state of charge. One uninterrupted cycle from 100% down to automatic shutdown and back to 100% resets the coulomb counter against the new cell's actual curve.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the modem's minimum voltage threshold under peak load, even though the fuel gauge still shows charge remaining. A fresh cell on an uncalibrated fuel gauge IC is the most common cause — the counter does not yet know where the real voltage cliff sits on this cell's curve. Run the recalibration cycle described above first. If shutdowns continue after one full cycle, check that the battery connector is fully seated, as a high-resistance contact causes the same voltage sag under load.