BA721 Meilan Note 6 Compatible Battery 3.85V 3900mAh

Meilan Note 6 / M5 Note — 3.85V Li-Polymer Replacement Battery (BA721)

The BA721 is a 3.85V, 3900mAh Li-Polymer cell that replaces the original power unit in the Meilan Note 6, M5 Note, M5 Note Global DualSIM, and M5 Note Global DualSIM TD-LTE. It fits the same connector and footprint as the factory cell. Capacity is rated at 15.02Wh.

• Note 6 and M5 Note platform compatibility: These models share the same chassis layout, battery connector pinout, and fuel gauge IC — the BA721 part number covers all four variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Meilan M5 Note unit. The BMS accepted the charge IC handshake correctly and held voltage above 3.6V through the bulk of the discharge curve with no unexpected cutoffs.
• First-cycle fast charge caution: After installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging runs against an uncalibrated reference.

Why the Note 6 reports wrong battery percentage after a cell swap

The Qualcomm PMIC in the M5 Note platform uses a coulomb counter that builds a capacity model from repeated charge and discharge cycles. When a new cell goes in, the counter still references the old cell's learned curve. The result is percentage readings that jump, stall, or show full charge when the cell is not actually full. One complete discharge down to automatic shutdown followed by an uninterrupted charge to 100% forces the fuel gauge IC to reset its baseline against the new cell's actual capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the BMS cutoff threshold under load — typically during modem activity, screen-on bursts, or navigation — even though the OS shows charge remaining. A new Li-Polymer cell can have slightly higher internal impedance on early cycles, causing a sharper voltage sag under peak draw than the fuel gauge anticipates. The BMS trips the protection circuit to prevent over-discharge. After three to five full cycles, internal impedance drops and the voltage cliff becomes less steep. If shutdowns persist past five cycles, check that the cell resting voltage after a full charge reads at or above 4.35V.