ADOC K1 Replacement Battery 3.7V 1200mAh Li-ion

ADOC K1 / K4 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1200mAh Li-ion cell for the ADOC K1 and K4 smartphones. It replaces the original battery when the phone stops holding charge, shuts down unexpectedly, or the cell has visibly swollen. Physical dimensions are 53.00 × 33.90 × 5.70mm — confirm these against your original before installing.

• K1 and K4 shared battery rail: Both models run the same 3.7V single-cell architecture with identical connector pinout and BMS handshake requirements. One cell covers both devices without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under screen-on and modem-active loads. The BMS held cutoff thresholds correctly and the charge IC accepted the cell without flagging a fault on the third cycle.
• 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 the new cell's discharge curve before high-current charging begins on an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on the replacement cell

The K1 and K4 fuel gauge IC retains the discharge curve from the old, degraded cell. When the new cell still shows 20–30% on the status bar, the IC's voltage model may already be predicting imminent cutoff based on stale data. Under modem or display load, the phone pulls enough current to trigger the BMS low-voltage lockout before the percentage reaches zero. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and aligns the gauge to the new cell. After that cycle, shutdowns at high percentages should stop.

Device will not power on after the battery sat discharged in storage

Li-ion cells that self-discharge below approximately 2.5V trigger BMS lockout — a hard protection state that blocks current flow to prevent cell damage. The phone shows no response to the power button and does not appear on a PC as a USB device. Connect it to a wall charger — not a PC port — and leave it for 15–20 minutes. The charge IC delivers a low trickle current to bring the cell above the BMS re-enable threshold, at which point normal charging resumes and the phone will power on.