Fly IQ4405 Replacement Battery BL7203 3.7V 1000mAh

Fly IQ4405 / IQ4413 — 3.7V Li-ion Replacement Battery (BL7203)

This is a 3.7V Li-ion cell rated at 1000mAh (3.7Wh), built to the BL7203 specification. It fits the Fly IQ4405 and IQ4413 smartphones. If your original battery swells, refuses to hold charge, or drops suddenly under load, this is the direct swap.

• IQ4405 and IQ4413 compatibility: Both handsets share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The BL7203 part number covers both models — no adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the IQ4405 platform. The BMS accepted the cell without fault flags, and the charge IC progressed normally through CC and CV phases to termination.
• Fuel gauge recalibration on first use: 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 reporting accurate percentages to the OS.

Sudden shutdown at 20–30% on a new BL7203 cell

This happens when the fuel gauge IC is still calibrated to the old cell's voltage curve. The new cell hits a steeper voltage cliff under modem or screen load, and the phone interprets that drop as a critical low-battery event. It is not a defective cell — it is a calibration mismatch. Run two full discharge-charge cycles without interruption and the shutdowns should stop. After the second cycle, check that the battery reports 4.15–4.20V at a full charge reading.

Phone reporting wrong battery percentage after cell swap

The coulomb counter inside the fuel gauge IC retains data from the old cell. After installing the BL7203, the OS reads percentage against a curve that no longer matches the physical cell. The fix is a forced recalibration: drain the battery until the phone shuts off on its own, then charge uninterrupted to 100%. One full cycle is usually enough to resync the reported percentage with actual cell state. If the percentage still jumps erratically after two cycles, check the battery contacts for debris or slight misalignment.