Redmi Note 10 BN59 Replacement Battery 3.87V 4800mAh

Redmi Note 10 / M2101K7AI / M2101K7AG — 3.87V Li-Polymer Replacement Battery (BN59)

This is a 3.87V, 4800mAh Li-Polymer battery built to replace the original BN59 cell in the Redmi Note 10 (M2101K7AI, M2101K7AG). It fits the phone physically and electrically — same connector, same voltage rail, same form factor at 87.20 × 63.00 × 5.10mm. If your current cell swells, drops charge fast, or won't hold voltage under load, this is the direct swap.

• Note 10 model variants (M2101K7AI / M2101K7AG): Both variants share the same BN59 battery specification — identical voltage rail, connector pinout, and BMS handshake requirements. One replacement covers both regional builds without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the Note 10 platform. The BMS accepted the charge IC handshake correctly, thermal cutoff triggered within expected thresholds, and the fuel gauge IC began tracking the new discharge curve after the first full cycle.
• First cycle fast-charge protocol: After installation, disable fast charging for the first complete discharge-charge cycle. The fuel gauge IC on the Note 10 is calibrated to the old cell's discharge curve. Running fast charging before one full recalibration cycle pushes high current into an uncalibrated cell, which can lock in percentage reporting errors from the start.

Why the Note 10 reports wrong battery percentage after a cell swap

The Note 10 uses a coulomb counter tied to the fuel gauge IC, which stores the discharge curve of the original BN59 cell in memory. When you install a new cell, that stored curve no longer matches the actual cell chemistry. The IC continues estimating state-of-charge against the old data, so displayed percentage drifts away from real voltage. One full discharge to auto-shutdown followed by an uninterrupted charge to 100% forces the IC to rewrite the curve against the new cell. After that cycle, percentage accuracy stabilises.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage-cliff failure — not a capacity problem. Under high load (mobile data, screen at full brightness, active apps), the cell voltage drops faster than the fuel gauge IC predicts, crossing the BMS cutoff threshold while the display still shows 20–30% remaining. It happens most often in the first few cycles before the IC has mapped the new cell's real discharge curve. Run one full calibration cycle — discharge to auto-shutdown, charge uninterrupted to 100% — and avoid heavy multitasking during that cycle. If shutdowns persist after two full cycles, check that the battery connector is fully seated, as a loose pin raises contact resistance and accelerates voltage sag under load.