Telstra GC900f Replacement Battery 3.7V 900mAh Li-ion

Telstra GC900f — 3.7V Li-ion Replacement Battery

This 3.7V, 900mAh Li-ion cell replaces the original battery in the LG GC900f (sold under the Telstra brand). It fits both the GC900f and GC-900f variants. The cell matches the original voltage rail and physical dimensions — 46.86 × 37.01 × 5.39mm — for a direct fit in the battery bay.

• GC900f and GC-900f compatibility: Both model designations refer to the same hardware platform. They share an identical battery bay, connector pinout, and charge IC interface — this cell works across both without modification.
• Bench tested on actual hardware: We cycled this cell through charge and load on the GC900f platform. The BMS accepted the cell without a handshake error, and the charge IC completed a full cycle without thermal cutoff or early termination.
• Fuel gauge recalibration on first use: After fitting this cell, run one full discharge to automatic shutdown before recharging. The GC900f's fuel gauge IC was calibrated to the old cell's discharge curve — skipping this step causes the percentage readout to drift or jump erratically during normal use.

Sudden shutdown at 20–30% on the GC900f after a cell swap

The GC900f shuts down mid-use — not because the cell is empty, but because it cannot hold voltage under the combined load of the modem radio and screen backlight. A new cell with a slightly different internal resistance curve hits a voltage cliff the BMS reads as a cutoff condition before the fuel gauge catches up. This is common in the first two or three cycles on a replacement cell. Running one complete discharge-charge cycle without interruption lets the coulomb counter resync to the new cell's actual capacity and resistance profile. After that, shutdowns at 20–30% reported charge should stop.

Phone feels warm near the battery compartment during first charge

A new high-impedance cell dissipates more heat during the constant-current phase of charging than a worn cell does. On the GC900f, the charge IC doesn't reduce current for a new cell — it pushes the same current it used on the degraded original. This is normal for the first one or two cycles and not a sign of a faulty cell. If warmth continues past the third full charge, check that the battery contacts are clean and making full contact — a dirty contact increases resistance and adds heat at the interface point.