BT68 Meizu M3 Replacement Battery 3.85V 2800mAh

MeiZu M3 / M688 Series — 3.85V Li-Polymer Replacement Battery (BT68)

This is a 3.85V, 2800mAh Li-Polymer replacement cell for the MeiZu M3 smartphone and its M688U, M688Q, and M688M variants. It slots in when the original BT68 has lost capacity or swollen beyond safe use. Capacity figure matches the OEM spec at 10.78Wh.

• M3 and M688 variant compatibility: The M688U, M688Q, and M688M share the same physical footprint, connector pinout, and BMS handshake protocol as the base M3. One cell covers all of them because the voltage rail and charge IC communication lines are identical across that production run.
• Bench tested on actual hardware: We ran this cell through the MeiZu charge IC handshake and confirmed BMS recognition on first connection. The protection circuit responded correctly to both low-voltage cutoff and charge-termination signals without requiring a manual reset.
• 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 coulomb counter — which is what causes erratic percentage readings in the first day of use.

Why the MeiZu M3 reports wrong battery percentage after a cell swap

The M3 uses a coulomb counter IC that builds its reference model from the previous cell's charge and discharge history. When you swap in a new cell, that stored model no longer matches the actual cell chemistry. The mismatch shows up as jumpy percentage readings or a figure that stays frozen for long stretches. One full discharge down to automatic shutdown, followed by an uninterrupted charge to 100%, forces the IC to rebuild its reference against the new cell curve.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff, not a capacity problem. Under peak load — mobile data handoff, screen at full brightness, or a background sync — the cell voltage sags below the BMS cutoff threshold even though the fuel gauge still shows charge remaining. It happens most often in the first few cycles when the gauge IC hasn't finished calibrating. Run two full discharge-charge cycles without fast charging and monitor whether the shutdown point moves lower. If it persists past three cycles, check that the cell connector is fully seated — a high-resistance connection amplifies voltage sag under load.