Gigabyte GSmart MS804 Replacement Battery 3.7V 1200mAh

Gigabyte GSmart MS804 / Helen — 3.7V Li-ion Replacement Battery (AZK40-HEL090-ZOR)

This is a 3.7V 1200mAh Li-ion replacement battery for the Gigabyte GSmart MS804 and Helen smartphones. It carries OEM part number AZK40-HEL090-ZOR and slots into the same battery bay as the original cell. Voltage and capacity match the factory spec exactly — no modifications needed.

• GSmart MS804 and Helen compatibility: Both models share the same battery bay dimensions (65.25 × 38.84 × 5.64mm), identical 3.7V nominal voltage rail, and the same connector orientation. One cell fits both variants without adaptation.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS communicated correctly with the charge IC, accepted current at the expected rate, and held voltage within spec across the full discharge curve.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard rate. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging begins on an uncalibrated gauge.

Sudden shutdown at 20–30% on the GSmart MS804 after a cell swap

This is a fuel gauge calibration problem, not a faulty cell. The fuel gauge IC on the MS804 retains the discharge curve of the old degraded cell. When the new cell hits a voltage point the IC associates with 20–30% on the old curve, it cuts power to protect the system — even though the new cell still has charge left. The fix is a single full discharge to near 0% and a full uninterrupted charge back to 100%. After that cycle, the coulomb counter recalibrates to the new cell and percentage reporting stabilises.

Phone stays off after sitting in a drawer for months — won't power on

Li-ion cells self-discharge in storage. If the MS804 sat unused for an extended period, the cell voltage may have dropped below 2.5V — the threshold where the BMS locks out to prevent damage. The phone will show no response to the power button. Connect the phone to a wall charger using the original cable and leave it for 15–20 minutes without pressing anything. Once the charge IC pushes enough current to bring the cell above 3.0V, the BMS releases its lockout and the phone will power on or show a charging indicator.