MeiZu MX6 BT65M Replacement Battery 3.8V 3000mAh

MeiZu MX6 / M685 Series — 3.8V Li-Polymer Replacement Battery (BT65M)

This is a 3.8V, 3000mAh (11.4Wh) Li-Polymer cell built to replace the original BT65M battery in the MeiZu MX6 smartphone. It fits the M685Q, M685C, and M685U variants as well — all share the same battery bay dimensions and connector pinout. Use the capacity figure above; it is confirmed from product data.

• MX6 and M685 platform fit: The M685Q, M685C, and M685U all use the same 77.80 × 65.70 × 3.70 mm footprint, matching BT65M connector and BMS communication lines. Swapping between these variants does not require any hardware modification.
• Bench tested on actual hardware: We ran this cell through full charge and load cycles on the MX6 platform. The BMS handshake completed without error flags, charge current stepped correctly through CC and CV phases, and the protection circuit tripped at expected over-current thresholds.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the Coulomb counter IC a clean reference cycle against the new cell's actual discharge curve before high-current charging begins.

Sudden shutdown at 20–30% on the MX6 after a cell swap

The MX6's fuel gauge IC was calibrated to the discharge curve of the original aged cell. A new cell has a steeper voltage cliff at low state-of-charge, so the IC triggers a low-voltage shutdown before the percentage display reaches zero. This is not a defective battery — it is a calibration mismatch. Run one full uninterrupted discharge to automatic cutoff, then charge to 100% without interruption. After that cycle, the Coulomb counter resets its end-of-discharge voltage reference to match the new cell, and shutdowns at 20–30% stop.

MeiZu fast charge not accepted by the BMS on the first cycle after replacement

On first contact with a charger, the BMS in a new cell defaults to standard 5V/1A until it completes one full charge cycle and verifies cell integrity. The MX6 charge IC will not negotiate the higher voltage rail until the BMS releases that lock. Do not assume the battery or charger is faulty. Complete one full standard-rate charge from flat to 100%, and fast charge will be available from the second cycle onward. If it still does not activate, confirm the charger output with a USB meter — the port must present at least 9V/1.67A to trigger the fast-charge handshake.