About this replacement
MeiZu M5s Series — 3.85V Li-Polymer Replacement Battery (BA612)
This is a 3000mAh, 3.85V Li-Polymer replacement cell for the MeiZu M5s smartphone. It fits the M5s, M5s Dual SIM, M5s Dual SIM TD-LTE, and M612M variants — all models that use the BA612 battery. Capacity is 11.55Wh, matching the original cell specification.
- M5s variant compatibility: The M5s, M5s Dual SIM, and M5s Dual SIM TD-LTE share the same physical bay, connector pinout, and BMS communication protocol — one cell covers all three. The BA612 part number is the key identifier across these variants.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on an M5s unit. The BMS handshake completed correctly on first boot, charge current ramped as expected, and the protection circuit triggered at the correct low-voltage threshold without nuisance cutoffs.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first day.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff problem, not a capacity problem. Under peak load — active LTE modem, screen at full brightness, background sync — the cell voltage drops faster than the fuel gauge predicts. The phone shuts off because cell voltage hits the BMS cutoff floor even though the OS still shows charge remaining. One full discharge-charge cycle without fast charging lets the coulomb counter recalibrate against the actual discharge curve of the new cell, and the shutdowns typically stop after that.
Phone not powering on after the battery sat in storage
Li-Polymer cells self-discharge slowly in storage. If the cell dropped below 2.5V per cell, the BMS enters lockout mode and the phone will not respond to a short press of the power button. Connect the phone to a 5V charger and leave it for 20–30 minutes without pressing anything — the charge IC needs to trickle current into the cell before the BMS will release the lockout and allow a normal boot. If the charging indicator appears, the cell is recovering. If there is no response after 40 minutes, check the charging cable and adapter output with a different device first before drawing further conclusions about the cell.