About this replacement
Lenovo Vibe K6 Power — 3.85V Li-Polymer Replacement Battery (BL272)
This is a 3.85V, 4000mAh Li-Polymer replacement battery for the Lenovo Vibe K6 Power (K33A42). It replaces OEM part numbers BL272 and SB18C10605. Swap it in when the original cell no longer holds a charge through a normal day of use.
- Vibe K6 Power and K33A42 fitment: Both model designations share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The BL272 cell fits either variant without modification — the fuel gauge IC reads the same communication lines on both boards.
- Bench tested on actual hardware: We cycled this cell on a K33A42 board and confirmed the BMS accepted the new cell without a fault flag. Charge current ramped normally through CC and CV phases, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
- 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 map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated reference.
Sudden shutdown at 20–30% on the Vibe K6 Power after a cell swap
This happens because the fuel gauge IC is still using the old cell's voltage-to-capacity curve. When the modem transmits or the screen brightness spikes, current draw pulls the cell voltage down sharply. The IC reads that voltage drop against the wrong curve and sees it as a critical low-voltage event, triggering an emergency shutdown. The fix is one full uninterrupted discharge to 0% followed by a full charge to 100% with fast charging off. After that cycle, the coulomb counter resets to the new cell's actual capacity floor.
Battery percentage jumping erratically after replacement
Erratic percentage jumps — for example, 45% dropping to 12% in under a minute — point to a fuel gauge IC that has not yet recalibrated to the new cell. The IC's stored charge table was built around the degraded original cell and no longer maps accurately to a fresh 4000mAh cell. Run two full discharge-charge cycles with the screen on and mobile data active to force real-load recalibration. After the second cycle, reported percentage should track actual cell voltage within a few points at 3.85V nominal.