Li3936T44P6h836542 Nubia M2 Replacement Battery 3.85V 3600mAh

Nubia M2 / NX551J — 3.85V Li-Polymer Replacement Battery (Li3936T44P6h836542)

This is a 3.85V, 3600mAh Li-Polymer cell built to replace the original battery in the Nubia M2, M2 Dual SIM, M2 Dual SIM TD-LTE, and NX551J smartphones. It matches the OEM part number Li3936T44P6h836542 and fits the same 80.80 × 64.54 × 4.02mm cavity. Use this when the original cell no longer holds charge or swells.

• M2 and NX551J platform fit: All four listed variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers the whole lineup without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the NX551J. The BMS accepted the cell, passed the protection IC handshake, and held voltage above 3.6V through standard load cycles including sustained LTE data and display-on draws.
• Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This lets the fuel gauge IC map its coulomb counter to the new cell's actual discharge curve before fast charge current is applied to an uncalibrated cell.

Why the Nubia M2 reports wrong battery percentage after a cell swap

The NX551J uses a fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell chemistry or internal resistance. The gauge continues calculating percentage against old data, so readings drift — sometimes reading 60% when the cell is already near cutoff voltage. One full uninterrupted discharge-charge cycle forces the IC to rebuild its reference table against the new cell. After that cycle, percentage tracking stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under high instantaneous load — typically the modem transmitting or the display at full brightness — before the fuel gauge IC predicts it should. A new cell with a slightly different voltage curve hits the BMS undervoltage cutoff at roughly 3.2–3.3V while the gauge still shows 20–30% remaining. The fix is the same recalibration cycle: discharge to automatic shutdown and charge to 100% without interruption. After one full cycle, the gauge threshold and actual cell voltage align.