Fly IQ4514 Replacement Battery BL3819 3.8V 1800mAh

Fly IQ4514 Quad EVO Tech 4 — 3.8V Li-Polymer Replacement Battery (BL3819)

This is a 3.8V, 1800mAh Li-Polymer replacement battery for the Fly IQ4514 and IQ4514 Quad EVO Tech 4 smartphones. It replaces OEM part number BL3819. Use this when the original cell no longer holds charge or the phone shuts down unexpectedly under load.

• IQ4514 and IQ4514 Quad EVO Tech 4 compatibility: Both variants use the same BL3819 cell format — identical voltage rail, connector pinout, and BMS handshake. One replacement covers both models without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the IQ4514 platform. The BMS accepted the charge IC handshake on the first cycle and held voltage within spec under simultaneous screen-on and modem load.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-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 cell.

Sudden shutdown at 20–30% on the IQ4514 after a cell swap

This happens because the fuel gauge IC is still referencing the discharge curve of the old, degraded cell. The new cell has a steeper voltage drop near the lower end of its curve than the worn cell did. When the modem fires during a call or data transfer, voltage sags below the shutdown threshold before the gauge reads zero. The fix is one full discharge cycle with the screen on — let it run until the phone powers off on its own, then charge to 100% uninterrupted. After that cycle, the coulomb counter recalibrates to the new cell and percentage readings stabilise.

Phone will not power on after the BL3819 sat in storage

Li-Polymer cells self-discharge over time. If the cell dropped below roughly 2.5V per cell during storage, the BMS enters lockout mode and blocks all charge current to prevent thermal runaway on a deeply discharged cell. Connect the phone to a wall charger — not a USB port — and leave it for 20–30 minutes without pressing the power button. The charge IC trickle-charges the cell at a low current rate to bring it back above the BMS recovery threshold, typically around 3.0V, at which point normal charging resumes and the phone boots.