BN44 Xiaomi Redmi 5 Plus Replacement Battery 3.85V 3900mAh

Xiaomi Redmi 5 Plus — 3.85V Li-Polymer Replacement Battery (BN44)

This is a 3.85V, 3900mAh (15.02Wh) Li-Polymer cell that replaces the OEM BN44 battery in the Xiaomi Redmi 5 Plus, including MEG7, MEE7, and Dual SIM variants. It fits the same footprint at 85.45 × 64.00 × 3.90mm and connects to the same BMS handshake the phone's charge IC expects. Install it when the original cell swells, drains abnormally fast, or won't hold a charge.

• Redmi 5 Plus variant coverage: The MEG7, MEE7, and Dual SIM models all run the same 3.85V power rail with the same BN44 connector and BMS protocol. One cell covers all variants — no hardware or firmware differences affect compatibility.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Redmi 5 Plus platform. The BMS accepted the handshake on the first cycle, and the charge IC held current within spec throughout — no cutoff trips or thermal flags.
• First-cycle fuel gauge reset: After installation, disable fast charging and let the phone complete one full discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before any high-current charging pushes into an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the Redmi 5 Plus after a cell swap

A new cell has a different internal resistance profile than the degraded one the fuel gauge IC was calibrated against. When modem activity or screen brightness spikes load current, the cell voltage dips faster than the old discharge curve predicts — the phone sees what looks like a voltage cliff and cuts power to protect the SoC. This isn't a faulty battery. It's the coulomb counter firing against stale calibration data. One full discharge from 100% down to automatic shutdown, followed by a complete charge, is enough to recalibrate. The shutdowns stop once the fuel gauge has a real map of the new cell.

OS percentage jumping erratically in the first few days after replacement

The Redmi 5 Plus fuel gauge IC stores a learned discharge curve for the installed cell. Swap the cell and that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The result is percentage readings that jump — sometimes 10–15 points in either direction — as the IC tries to reconcile measured voltage against an outdated model. Two to three full discharge-charge cycles at standard charge rate correct this. After that, the IC locks onto the new curve and percentage tracking stabilises. If jumping continues past three cycles, check that fast charging is disabled during calibration — high-current input skews coulomb counter readings.