Ecom Ex-Handy 04 Replacement Battery 3.7V 900mAh

Ecom Ex-Handy 04 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion battery for the Ecom Ex-Handy 04 rugged smartphone. It fits the Ex-Handy 04 directly and restores power capacity when the original cell has degraded. Capacity is 3.33Wh — identical to the factory specification.

• Ex-Handy 04 fit: The Ex-Handy 04 uses a fixed 3.7V single-cell Li-ion configuration with a dedicated connector and BMS handshake tied to that voltage rail. This replacement matches those parameters so the charge IC and protection circuit communicate correctly with the device.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on bench equipment and monitored BMS communication at each stage. The protection circuit responded correctly to cutoff thresholds — no false trips, no thermal flags under normal load.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to 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 replacement cell

This happens because the fuel gauge IC is still running the discharge curve from the old, degraded cell. The new cell has a steeper voltage cliff at low charge states — the phone's modem or screen pulls enough current to drop the cell voltage below the BMS cutoff threshold before the reported percentage reaches zero. The OS sees a valid percentage but the cell voltage has already collapsed under load. One full discharge-to-shutdown followed by a full uninterrupted charge corrects this — the coulomb counter resets to the new cell's actual curve.

Phone won't power on after the battery sat in storage

Li-ion cells self-discharge during storage. If the cell drops below approximately 2.5V, the BMS enters lockout mode and blocks charge current to prevent damage to a deeply discharged cell. The phone shows nothing when connected to a charger. Connect the device to a wall adapter — not a PC USB port — and leave it for 15–20 minutes without pressing the power button. Most BMS circuits on this cell class include a trickle-recovery path that slowly raises cell voltage back above the 2.5V re-initialisation threshold before allowing normal charge current.