BL207 Lenovo K900 Replacement Battery 3.7V 2500mAh

Lenovo K900 / K100 — 3.7V Li-Polymer Replacement Battery (BL207)

This is a 3.7V, 2500mAh Li-Polymer cell sourced to OEM part number BL207. It fits the Lenovo K900 and K100 Android smartphones. At 9.25Wh and 110.91 × 46.70 × 3.28mm, it matches the original physical and electrical spec of both models.

• K900 and K100 compatibility: Both models use the same BL207 cell with identical connector pinout, voltage rail, and BMS handshake. The charge IC on each device expects the same 4.2V cutoff and protection circuit response — one cell covers both.
• Bench tested on actual hardware: We ran the BL207 through a full discharge-charge cycle on the K900. The BMS accepted the cell without fault flags, charge current stepped down correctly at 4.2V, and the protection circuit tripped at the expected low-voltage cutoff threshold.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. The K900's fuel gauge IC is calibrated to the old cell's discharge curve — this single cycle lets the coulomb counter reset its reference against the new cell before high-current charging begins.

Why the K900 reports wrong battery percentage after a cell swap

The K900 uses a coulomb-counting fuel gauge IC that builds its state-of-charge model from accumulated charge and discharge data on the old cell. When the cell changes, that learned curve no longer matches the new cell's actual capacity and impedance profile. The reported percentage can read 20–30% higher or lower than real charge state for several cycles. One full uninterrupted discharge down to automatic shutdown, followed by a full charge to 100%, forces the IC to re-anchor its reference points to the new cell.

Sudden shutdown at 20–30% remaining on the K900

This is a voltage cliff, not a capacity problem. Under peak modem or screen load, the cell voltage sags below the BMS cutoff threshold even though the fuel gauge still reads charge remaining. On an aged or newly installed cell with an uncalibrated gauge, this gap between reported and actual state-of-charge widens. Run one full calibration cycle first — discharge to auto-shutdown, charge uninterrupted to 100%. If shutdowns continue after two calibration cycles, check that the battery connector is fully seated and measure open-circuit voltage above 3.7V before reinstalling.