AT&T Mobile Hotspot Pro W-20 Replacement Battery 3.85V 4750mAh

AT&T Mobile Hotspot Pro — 3.85V Li-ion Replacement Battery (W-20)

This is a 3.85V, 4750mAh Li-ion replacement battery for the AT&T Mobile Hotspot Pro (W-20). It fits directly into the Mobile Hotspot Pro, restoring power to the device that creates a shared personal Wi-Fi network over cellular data. Capacity matches the original specification at 18.29Wh.

• Mobile Hotspot Pro fit: The W-20 part number ties this battery to the Mobile Hotspot Pro's specific connector and BMS handshake. The device runs a combined cellular modem and Wi-Fi radio load simultaneously, so the battery must negotiate correctly with the onboard protection circuit or the hotspot shuts down under draw.
• Bench tested on actual hardware: We ran this battery under a simulated multi-device Wi-Fi load combined with active LTE data. The BMS held the output rail stable through connection peaks and did not trip on the combined radio draw spike at session start.
• Ventilation during extended sessions: Keep the hotspot on a hard, flat surface with clear airspace around it during long sessions. When connected devices are at the edge of Wi-Fi range, the radio amplifier runs at maximum output, generating sustained heat that accelerates cell wear if the unit sits on fabric or in a pocket.

Why the Mobile Hotspot Pro drops connections mid-session at full capacity

When the hotspot reaches its maximum connected device count, the Wi-Fi controller and cellular modem draw peak current simultaneously. If the battery's internal resistance is elevated — common in a degraded original cell — voltage sags below the modem's operating threshold for a fraction of a second. The modem resets, and all connected devices lose the session. A fresh cell with lower internal resistance maintains the voltage rail through those combined load spikes, preventing the modem reset.

Hotspot won't power on after sitting unused for several weeks

Li-ion cells self-discharge during storage. If the Mobile Hotspot Pro sat unused long enough, the battery voltage dropped below the minimum boot threshold — typically around 3.0V per cell — and the BMS locks the output to protect the cell from damage. The device shows no response to the power button because the BMS has cut the circuit entirely. Connect the hotspot to a charger and leave it for at least 20–30 minutes before attempting to power on; the charger wakes the BMS and brings the cell back above the 3.0V recovery threshold.