Telstra 5G Wi-Fi Pro Replacement Battery 3.85V 4000mAh

Telstra 5G Wi-Fi Pro — 3.85V Li-Polymer Replacement Battery

This 3.85V, 4000mAh (15.4Wh) Li-Polymer battery replaces the original cell in the Telstra 5G Wi-Fi Pro mobile hotspot. It restores full portability when the factory battery no longer holds a usable charge. The 5G Wi-Fi Pro uses this cell to power both the 5G modem and the Wi-Fi broadcast radio simultaneously.

• 5G Wi-Fi Pro fit: The 5G Wi-Fi Pro runs two radio stacks off a single cell — the 5G modem and the Wi-Fi AP. Both draw from the same 3.85V rail, so the replacement cell must match the original voltage and physical footprint exactly. This battery does both at 80.80 × 50.26 × 7.50mm.
• Bench tested on actual hardware: We ran this cell under combined 5G modem and Wi-Fi load with eight client devices connected. Voltage held above 3.6V through the discharge curve and the BMS did not trigger a protective cutoff under normal session draw.
• Ventilation during extended sessions: Keep the hotspot on a hard, flat surface — not a couch cushion or bag pocket. When connected devices are far from the hotspot, the cellular radio pushes to maximum transmit power. That heat accumulates inside the enclosure and directly stresses the battery cell over time.

Why the 5G Wi-Fi Pro drops connections mid-session on a new battery

The 5G modem and the Wi-Fi radio both spike current draw at the same moment — the modem is retransmitting data while the Wi-Fi stack is servicing multiple clients. A worn or undersized cell sags below the BMS cutoff threshold during that combined peak, and the device resets. A fresh 4000mAh cell with a healthy internal resistance profile sustains that dual-radio spike without the voltage floor dropping far enough to trigger a cutoff. If drop-outs persist after battery replacement, check whether the hotspot is at the edge of 5G coverage — signal hunting multiplies modem draw significantly.

Hotspot shows a charge indicator but will not boot after sitting unused

Li-Polymer cells self-discharge slowly during storage. If the 5G Wi-Fi Pro has been sitting unused for several weeks, the cell may have dropped below the minimum boot voltage — typically around 3.0V — even if the LED still flickers. The BMS may also enter a locked low-voltage state that blocks normal charging. Connect the hotspot to a wall charger and leave it for 20–30 minutes before attempting to power it on; this allows the charger to trickle-raise the cell above the BMS re-initialisation threshold of approximately 3.2V.