About this replacement
Redmi K60 — 3.87V Li-Polymer Replacement Battery (BM5M)
This is a 3.87V, 5400mAh Li-Polymer replacement battery for the Redmi K60 smartphone. It carries OEM part number BM5M and fits directly into the K60's battery bay. Capacity is rated at 20.9Wh, matching the original cell specification.
- Redmi K60 fit: The K60 uses a dedicated battery bay sized for the BM5M form factor — 88.60 x 65.00 x 5.10mm. The connector pinout and BMS communication lines match the K60's charge IC, so the fuel gauge IC can read the cell state correctly once calibrated.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the K60 platform. The BMS accepted the charge IC handshake cleanly, and the coulomb counter tracked state-of-charge without dropout or false full-charge flags on the first complete cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated cell — preventing erratic percentage readings from the first session.
Why the K60 reports wrong battery percentage after a cell swap
The K60's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The IC reads voltage and maps it to the old curve, producing percentage values that are off by 10–20%. One full slow-rate discharge down to automatic shutdown, followed by a full charge to 100%, forces the coulomb counter to re-anchor its calibration to the new cell.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the BMS cutoff threshold under high instantaneous load — typically the modem during a call or the display at peak brightness — while the fuel gauge still reports 20–30% remaining. The old discharge curve told the IC that 3.6V meant 25% charge; with a new cell whose voltage curve sits differently, the real cut-off voltage arrives earlier than the IC expects. Run one complete calibration cycle first. If shutdown persists below 25%, check that the connector is fully seated — a high-resistance contact causes voltage sag under load and triggers BMS cutoff at 3.5V per cell.