360 N4 Replacement Battery QK-393 3.85V 3000mAh

360 N4 Series — 3.85V Li-Polymer Replacement Battery (QK-393)

This is a 3.85V, 3000mAh (11.55Wh) Li-Polymer cell replacing the QK-393 battery in the 360 N4 smartphone. It fits the N4, 1503-A01, and 1503-M02 variants. The physical dimensions are 73.40 × 63.10 × 3.90mm — measure your original cell before ordering if your device has been serviced before.

• N4, 1503-A01, and 1503-M02 compatibility: All three model numbers share the same battery bay geometry, connector pinout, and BMS handshake protocol — that is why one cell covers all three variants without modification.
• Bench tested on actual hardware: We ran the QK-393 replacement through full charge and load cycles on N4 hardware. The BMS accepted charge current correctly, thermal monitoring stayed within normal range, and the protection circuit tripped as expected at low-voltage cutoff.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still reading the old cell's discharge curve. A new Li-Polymer cell has a slightly different voltage-to-capacity slope. When the modem fires or the screen brightness spikes, the cell voltage dips below the threshold the gauge hasn't recalibrated for yet, and the device shuts off to protect the circuit. The fix is a full uninterrupted discharge down to automatic shutdown, followed by a full charge without interruption. After that single cycle, the coulomb counter resets against the new cell's actual curve and the shutdowns stop.

USB charging not recognised on the first plug-in after cell swap

After a cell swap, the charge IC sometimes fails to negotiate the correct charging profile on the first connection — the phone shows no charge icon or charges at a very slow rate. This occurs because the BMS on the new cell starts in a conservative low-current mode until it completes an initial handshake with the device's charge controller. Disconnect the cable, wait 30 seconds, then reconnect. If the issue persists after two reconnections, boot the phone fully before plugging in — this resets the charge IC negotiation stack and normal charging resumes.