Overmax Vertis Famy Replacement Battery 3.7V 1000mAh

Overmax Vertis Famy — 3.7V Li-ion 1000mAh Replacement Battery

This is a 3.7V Li-ion replacement battery rated at 1000mAh (3.7Wh) for the Overmax Vertis Famy smartphone. It slots directly into the Vertis Famy battery bay and connects to the phone's charge IC and fuel gauge circuit. No OEM part number is published for this cell, but the physical dimensions — 48.23 x 49.06 x 5.30mm — match the original cavity.

• Vertis Famy fit: The Vertis Famy runs a single-cell 3.7V Li-ion architecture with a compact form factor. This cell matches that voltage rail and fits the housing without modification to the connector or frame tabs.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a smartphone test rig. The BMS accepted charge handshake correctly, held voltage above 3.5V under screen and modem load, and cut off cleanly at the low-voltage threshold without triggering emergency shutdown prematurely.
• Fuel gauge recalibration after swap: On first use after installing this cell, disable fast charging and run one full discharge-to-charge cycle at standard rate. This lets the Vertis Famy's fuel gauge IC map its coulomb counter to the new cell's actual discharge curve before any high-current session runs against uncalibrated data.

Why the Vertis Famy reports wrong battery percentage after a cell swap

The Vertis Famy uses a fuel gauge IC that builds a discharge curve from repeated charge cycles on the original cell. When a new cell goes in, the IC still references that old curve. The mismatch causes the percentage readout to jump or stall — most visibly between 80% and 100%, and again near 20%. One full uninterrupted discharge from 100% down to automatic shutdown, followed by a full charge, forces the IC to recalculate against the new cell's actual impedance profile. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

This shutdown happens when the cell voltage drops sharply under load — modem transmit bursts and screen brightness spikes are the usual triggers. The phone's protection circuit reads the voltage sag as a critically low cell and cuts power before the OS can log a graceful shutdown. It is not a faulty cell — it is an uncalibrated fuel gauge reading surface charge instead of true state of charge. Run one complete discharge cycle at standard screen-on use with no fast charging, then recharge fully to 4.2V. After that calibration cycle, the gauge tracks cell voltage accurately under load and shutdown events at 20–30% typically stop.