Nexian IA-003 Compatible Battery 3.7V 1200mAh Li-ion

Nexian IA-003 / NX-IA-003 — 3.7V Li-ion 1200mAh Replacement Battery

This is a 3.7V 1200mAh lithium-ion battery for the Nexian IA-003 and NX-IA-003 smartphones. It replaces the original cell when capacity has dropped to the point where the phone no longer holds a useful charge. Dimensions are 53.18 × 34.00 × 6.80mm — confirm against your existing cell before fitting.

• IA-003 and NX-IA-003 fit: Both model designations share the same physical battery bay, connector pinout, and charge IC handshake. One cell covers both variants without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the IA-003 platform. The BMS accepted charge without fault flags, and voltage held stable across a full discharge curve with no mid-cycle cutoff.
• First-cycle recalibration on the IA-003: On first use, disable any fast-charge mode 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 Nexian IA-003 after a cell swap

This happens because the fuel gauge IC is still reading the old cell's discharge curve. The new cell hits a voltage cliff earlier than the IC expects — the phone cuts out before the percentage reaches zero. It is not a fault with the replacement cell. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and eliminates the early cutoff.

IA-003 showing erratic percentage jumps after battery replacement

The fuel gauge IC recalibrates in real time against the new cell during early cycles. Until it builds an accurate internal model, reported percentage can jump 5–15% between readings. This is a software state issue, not a defective cell. Run two full discharge-charge cycles without interruption and the readings stabilise — expect consistent reporting by the third cycle.