ZTE Nubia Red Magic 3s Li3949T44P6h996644 Compatible Battery 3.85V 4900mAh

ZTE Nubia Red Magic 3s — 3.85V Li-Polymer Replacement Battery (Li3949T44P6h996644)

This is a 3.85V, 4900mAh Li-Polymer replacement battery for the ZTE Nubia Red Magic 3s (NX629J) smartphone. It replaces OEM part Li3949T44P6h996644 and restores power to the display, processor, and all onboard systems. Fit this cell when the original no longer holds a full charge or fails to power the device.

• NX629J platform fit: The Red Magic 3s uses a fixed battery connector and BMS handshake tied to the NX629J board. This cell matches the physical footprint at 96.84 × 65.10 × 4.16mm and the 3.85V nominal voltage rail the charge IC expects.
• Bench tested on actual hardware: We ran this cell through charge and discharge on the NX629J board. The BMS accepted the cell, charge termination fired correctly at full voltage, and no protection trips occurred during load cycling on the display and modem.
• First cycle fast-charge protocol: After installation, disable fast charging and complete one full discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the Red Magic 3s after a battery swap

The NX629J fuel gauge IC retains the discharge curve from the old cell after a swap. When the new cell hits a voltage point the IC doesn't recognise, it reports remaining capacity incorrectly and can trigger a protective shutdown. This happens most often under modem or GPU load, where current draw causes a brief voltage sag the uncalibrated gauge reads as cell depletion. Run one full discharge to near-zero, then charge uninterrupted to 100% to let the coulomb counter reset its reference points.

USB-PD fast charge not activating on the first cycle after replacement

The Red Magic 3s charge IC negotiates fast-charge current with the BMS on the incoming cell before stepping up voltage. On a fresh cell at low state of charge, the BMS may limit current until it completes an initial validation handshake. This causes the phone to show standard charge speed even when plugged into a fast charger. Allow the first charge cycle to complete at whatever rate the system accepts — fast charging typically activates from the second cycle onward once the BMS clears the handshake.