About this replacement
ZTE Nubia Red Magic 6 Pro — 7.74V Li-Polymer Replacement Battery (Li3945T44P8H556490)
This 7.74V Li-Polymer battery replaces the original cell in the ZTE Nubia Red Magic 6 Pro (NX669J-P). It runs at 2200mAh / 17.03Wh and fits the same footprint as the OEM unit. If your phone shuts down early, charges to a lower percentage each cycle, or won't hold charge under gaming load, the cell has degraded and needs replacing.
- NX669J-P compatibility: The Red Magic 6 Pro uses a dual-cell Li-Polymer pack with a BMS that monitors individual cell voltage rails. This replacement matches the OEM cell configuration, connector pinout, and nominal voltage so the existing charge IC and BMS handshake without firmware errors.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge sequences on the NX669J-P board. The BMS accepted the cell on first contact, charge termination triggered correctly at 8.68V, and no thermal events occurred during the 65W fast-charge cycle.
- First-cycle fast charge precaution: On first use after installation, disable fast charging and complete one full discharge-to-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 state.
Sudden shutdown at 20–30% on the Red Magic 6 Pro after a cell swap
This happens when the fuel gauge IC is still using the discharge curve calibrated to the old, degraded cell. The new cell has a steeper voltage cliff at low state-of-charge, so the phone hits the hardware undervoltage cutoff before the OS percentage reaches zero. The phone reads 25% but the cell is already below the BMS floor voltage under display and modem load. One full discharge-to-charge cycle at standard rate forces the coulomb counter to resync against the new cell's actual curve — after that, shutdowns align correctly with the reported percentage.
OS reports battery percentage jumping erratically after replacement
Erratic percentage jumps are a fuel gauge IC recalibration issue, not a fault with the new cell. The coulomb counter accumulated error data from hundreds of cycles on the old cell and carries that into its first readings on the replacement. The IC needs a clean reference point. Run the phone from 100% down to automatic shutdown, then charge uninterrupted to 100% — this gives the fuel gauge IC a full capacity reference and stabilises percentage reporting from the next cycle onward.