KOMU K5 Replacement Battery 3.8V 2500mAh Li-Polymer

KOMU K5 — 3.8V Li-Polymer Replacement Battery

This 3.8V, 2500mAh (9.5Wh) lithium-polymer cell is a direct replacement for the KOMU K5 smartphone. It fits the K5's battery bay and connects to the same flex-ribbon connector used by the original cell. Voltage and capacity match the K5's power management IC requirements.

• K5 platform fit: The K5 uses a fixed battery bay with a single-wire BMS communication line. This cell's protection circuit matches that voltage rail and connector pinout, so the power management IC can read cell state correctly.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a K5 unit. The BMS accepted the cell on the first connection, charge termination triggered correctly at 4.35V, and the protection circuit tripped cleanly on over-discharge.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the charge IC pushes high current into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity fault. Under peak modem or screen load, the new cell's voltage briefly drops below the K5's low-voltage cutoff threshold — even though the fuel gauge still shows charge remaining. The fuel gauge IC was calibrated against the old cell's internal resistance curve, so it misreads how much voltage-under-load the new cell can sustain. Run two full discharge-charge cycles without fast charging to let the coulomb counter recalibrate, then verify the phone holds voltage above 3.5V under screen-on load.

Device not powering on after the battery sat in storage

Lithium-polymer cells in storage self-discharge slowly. If the cell drops below 2.5V, the BMS enters lockout to prevent damage — and the phone will not respond to a normal power-on press. Connect the K5 to a 5V charger and leave it for 15–20 minutes without pressing any button. The charge IC will trickle current into the cell until it clears the 2.5V lockout threshold, at which point normal charging resumes. If the charge LED does not appear after 30 minutes on the charger, check the cable and adapter output with a USB meter.