AT&T Unite W-5 Replacement Battery 3.7V 2500mAh

AT&T Unite W-5 — 3.7V Li-ion Replacement Battery (2500031)

This is a 3.7V, 2500mAh Li-ion battery for the AT&T Unite mobile hotspot (model W-5, UNITE-344B). It fits the original battery slot directly and restores power to the device after the factory cell degrades. Capacity figures come from the product data — 9.25Wh at 3.7V nominal.

• Unite and UNITE-344B fit: Both variants share the same W-5 battery platform — same voltage rail, same connector pinout, and the same BMS handshake sequence. One cell covers both units.
• Bench tested on actual hardware: We ran this cell through charge cycles on a Unite unit, monitoring BMS cutoff at both low-voltage protection (around 3.0V) and overcharge termination. The protection circuit tripped cleanly at both thresholds with no thermal events.
• Signal environment tip: In poor cellular coverage areas, the Unite's modem runs at maximum transmit power. That sustained radio draw generates more heat than normal use. Keep the hotspot out of enclosed spaces — a pocket or bag traps heat directly against the cell and accelerates capacity loss faster than typical charge cycling alone.

Hotspot warm during extended session — what's happening inside the battery

The Unite runs two radios simultaneously: the cellular modem and the WiFi transmitter. Under full load — maximum connected devices, weak signal area — both radios draw at peak output at the same time. That combined draw pulls higher current from the cell than typical light use, which raises internal resistance heating. The BMS monitors cell temperature and may throttle output before you notice reduced WiFi speeds. Keep the device flat on a hard surface, not face-down or inside a bag, so heat can dissipate through the casing.

Unite won't power on after sitting unused for weeks

Li-ion cells self-discharge at roughly 2–3% per month, but a partially depleted cell left in storage can drop below the minimum boot voltage the BMS will allow — typically 3.0V for this chemistry. The device won't power on because the BMS blocks discharge below that floor to protect the cell. Connect the Unite to the original charger and leave it for at least 30–45 minutes before attempting to power on. If the charge LED shows activity, the BMS has accepted the trickle charge and the cell voltage is recovering — boot once the indicator shows a partial charge state, confirmed by the status LED changing from red to amber.