Telstra 4GX Plus Replacement Battery 3.8V 2200mAh Li-Polymer

Telstra 4GX Plus — 3.8V Li-Polymer Replacement Battery (ICP37/54/72SA)

This 3.8V, 2200mAh Li-Polymer cell replaces the original battery in the Telstra 4GX Plus smartphone. It matches the OEM part number ICP37/54/72SA and fits the physical dimensions of the 4GX Plus battery bay at 70.25 × 53.77 × 4.00mm. Swap it in when the original cell no longer holds a charge or fails to power the device through normal daily use.

• 4GX Plus platform fit: The 4GX Plus uses a fixed voltage rail of 3.8V nominal with a BMS that checks cell impedance on power-up. This replacement cell matches that impedance profile, so the charge IC and fuel gauge IC initialise without fault codes on boot.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 4GX Plus charge IC. The BMS accepted the cell without cutoff events, and the coulomb counter began tracking state-of-charge correctly after one full cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins — skipping this step causes erratic percentage readings in the first few days.

Sudden shutdown at 20–30% on the replacement cell

A new Li-Polymer cell has a slightly different voltage-versus-capacity curve than the aged cell the fuel gauge IC was calibrated against. When the phone's modem fires up for a call or data burst, it pulls a short high-current spike. If the fuel gauge still thinks 25% charge equals a safe voltage, but the new cell dips below the cutoff threshold under that load, the phone shuts off immediately. One full discharge-charge cycle at standard rate lets the coulomb counter re-anchor its low-voltage cutoff point to the new cell. After that cycle, shutdowns at 20–30% stop.

Phone warm near the battery during the first few charges

A fresh Li-Polymer cell comes out of storage with higher internal impedance than a cell that has been cycled. The charge IC responds by pushing slightly more voltage to overcome that resistance, which generates heat at the cell surface. This is normal for the first two to three charge cycles and does not indicate a fault. If the device stays warm past the fourth full charge, check that the back cover is seated flat — any gap traps heat against the cell and keeps impedance elevated longer than it should.