Meizu Note 2 Replacement Battery BT42C 3.8V 3100mAh

MeiZu Note 2 — 3.8V Li-Polymer Replacement Battery (BT42C)

This is a 3.8V, 3100mAh (11.78Wh) Li-Polymer battery for the MeiZu Note 2 smartphone. It replaces part number BT42C directly. Fit it when the original cell degrades, loses capacity, or stops holding a charge entirely.

• MeiZu Note 2 fitment: The BT42C form factor is specific to this handset — 75.83 × 60.46 × 3.96 mm with a connector pinout that matches the Note 2 charge IC and fuel gauge IC. No other MeiZu model in this generation uses the same cell footprint and BMS handshake.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Note 2 motherboard and confirmed the BMS accepted the handshake without error flags. The charge IC ramped to full current and the fuel gauge IC tracked state-of-charge without dropout across three cycles.
• First-cycle fuel gauge recalibration: After fitting this battery, disable fast charging and run one complete discharge-to-charge cycle at standard rate. The fuel gauge IC on the Note 2 is calibrated to the old cell's discharge curve — one full slow cycle resets the coulomb counter against the new cell before high-current charging begins.

Why the Note 2 reports wrong battery percentage after a cell swap

The Note 2 uses a coulomb-counter fuel gauge IC that stores the discharge curve of the original cell in non-volatile memory. When a new cell goes in, the stored curve no longer matches the actual cell chemistry and impedance. The OS reads from that stale curve, so percentages display incorrectly — often reporting full charge well before the cell is actually topped off. One complete discharge below 10% and a full slow charge resets the learned curve to the new cell's actual profile.

Sudden shutdown at 20–25% on the replacement cell

This is a voltage cliff, not a capacity fault. Under combined modem and display load, the cell's internal resistance causes voltage to sag sharply at the low end of the discharge curve. The BMS reads that sag as a cutoff threshold breach and shuts the phone down even though the fuel gauge still shows charge remaining. It is most common in the first few cycles before the fuel gauge IC recalibrates. After two or three full discharge-charge cycles the gauge aligns the cutoff point to the new cell — shutdowns at 20–25% should stop by cycle three.