Redmi BM69 Replacement Battery 3.85V 6400mAh Li-Polymer

Redmi 24117RK2CC / K80 5G — 3.85V Li-Polymer Replacement Battery (BM69)

This is a 3.85V, 6400mAh Li-Polymer replacement battery for the Redmi Note 8 Pro (24117RK2CC) and the Redmi K80 5G. It uses OEM part number BM69 and slots into the same battery bay with the same connector and contact orientation. Capacity is 24.64Wh, matching the original cell specification.

• 24117RK2CC and K80 5G fitment: Both models share the BM69 form factor, connector pinout, and BMS handshake protocol. The fuel gauge IC on each device reads the same cell chemistry, so the replacement is recognized without triggering a hardware fault.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a BM69-compatible test rig. The BMS held cutoff at 4.35V on the charge ceiling and tripped protection at 2.8V on drain — both within spec. No thermal events occurred during fast-charge simulation.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes amps into an uncalibrated register.

Sudden shutdown at 20–30% on the BM69 replacement cell

This happens because the fuel gauge IC is still reading the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load before the reported percentage reaches zero. The phone interprets the voltage drop as an immediate low-voltage condition and shuts down to protect the SoC. Run one full discharge to below 5% and a full charge to 100% without interruption — this forces the coulomb counter to rewrite its baseline against the new cell.

USB fast charge not activating after battery replacement

On the first charge cycle after installation, the charge IC may not handshake with the proprietary fast-charge protocol because the BMS has not yet confirmed a stable cell state. The device defaults to standard 5V charging as a precaution. Charge the phone fully on standard charge first, then power cycle the device. Fast charging typically re-enables on the second charge cycle once the BMS has logged an initial full charge event.