AT&T Unite Pro 4G Replacement Battery 3.7V 2200mAh

AT&T Unite Pro / Aircard 781S — 3.7V Li-ion Replacement Battery (W-6, 5200080)

This 3.7V, 2200mAh Li-ion battery fits the AT&T Unite Pro, Unite Pro 4G, Unite Pro 4G LTE, and Aircard 781S mobile hotspots. It replaces the original cell when capacity has dropped and the device can no longer hold a charge through a full session. Voltage and connector match the OEM spec — no modifications needed to fit the battery compartment.

• Unite Pro and Aircard 781S compatibility: All four model variants in this line share the same 3.7V single-cell architecture, battery footprint, and connector pin-out. The BMS handshake is identical across the Unite Pro 4G and 4G LTE variants, so one replacement cell covers the full range.
• Bench tested on actual hardware: We ran this cell on the Aircard 781S under a simulated multi-device Wi-Fi load alongside active cellular data. The BMS held a stable discharge curve with no false low-voltage cutoffs at the modem draw peaks.
• Ventilation during extended hotspot sessions: Keep the Unite Pro on a hard, open surface when running extended sessions. When connected devices are far from the hotspot, the cellular radio pushes to maximum output power — that heat accumulates directly against the battery and accelerates cell degradation over time.

Hotspot disconnecting users mid-session on a new battery

The Unite Pro runs two power-hungry subsystems simultaneously — the cellular modem and the Wi-Fi radio. At maximum connections, the combined current draw creates brief voltage sag events. If the replacement cell has marginal internal resistance, the BMS interprets the sag as a low-voltage fault and cuts power to the modem, dropping all connected sessions. A cell meeting the original 2200mAh spec at proper internal resistance handles those peaks without triggering the cutoff. If disconnections persist, check that the battery contacts are clean and fully seated — a partial connection increases effective resistance at the terminal.

Unite Pro not powering on after sitting unused for several weeks

Li-ion cells self-discharge during storage, and the Unite Pro draws a small standby current even when powered off. Left long enough, the battery drops below the minimum boot voltage — typically around 3.0V for this cell — and the device will not respond to the power button. Connect the hotspot to a wall charger and leave it for at least 20 to 30 minutes before attempting to power on; most chargers will not output a fast-charge current until the cell recovers above 3.0V. If the indicator light never appears after 45 minutes on charge, the cell may have dropped below recoverable depth and requires replacement.