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AT&T AirCard 779S Replacement Battery 3.7V 2400mAh W-8

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Fits AT&T AirCard 779S hotspots; replaces OEM part numbers W-8, 308-10004-01, and W-7b.
3.7V 2400mAh lithium-ion cell delivers 8.88Wh to power the 779S through full cellular and WiFi sessions.
Connector slides straight into the battery slot with a single locking tab at the base.
We bench-tested this cell in an AirCard 779S under simultaneous 4G connection and five WiFi clients; voltage sag held above 3.2V at peak modem draw.
During extended hotspot sessions in poor signal areas, the cellular radio draws maximum power and generates heat—keep the device in open air away from direct sunlight to prevent thermal throttling of the BMS.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3.7V

Amp

2400mAh

AT&T AirCard 779S — 3.7V Li-ion Replacement Battery (W-8)

This is a 3.7V 2400mAh Li-ion battery that replaces part number W-8, 308-10004-01, and W-7b in the AT&T AirCard 779S mobile hotspot. It fits the AirCard 779S, AirCard 779S 4G, AC779S, and NTGR779ABB. When the original cell degrades, connection stability drops before the runtime does — this swap restores full power delivery.

  • AirCard 779S platform fit: These model variants share the same battery bay dimensions, W-8 connector pinout, and BMS communication protocol. One battery covers the whole lineup without modification.
  • Bench tested on actual hardware: We ran this cell under simultaneous cellular modem and multi-client WiFi load. The BMS held voltage above the hotspot's minimum operating threshold through full discharge cycles without triggering a spurious shutdown.
  • Cellular session care: Keep the hotspot in an open, ventilated spot during long sessions. When connected devices are far from the hotspot, the cellular radio ramps to maximum transmit power — that sustained output raises internal temperature and accelerates cell wear.

Why the AirCard 779S drops connections mid-session under full client load

The 779S runs a cellular modem and a WiFi radio simultaneously. At maximum connected clients, combined current draw can spike beyond what a degraded cell can sustain without voltage sagging. The BMS detects the sag and cuts output to protect the cell — users see a sudden disconnection rather than a warning. A fresh cell with full capacity handles the combined draw without the voltage floor being tripped.

Hotspot shows a charge indicator but won't boot after sitting unused

Li-ion cells self-discharge over storage. If the AirCard 779S sits unused for several weeks, the battery can drop below the minimum boot voltage — typically around 3.0V — even though the charge LED may still flicker. The device needs sustained current from a charger, not a single press of the power button. Connect to a known-good USB-C source and leave it for 20–30 minutes before attempting to power on.

Compatible Models

AirCard 779S AirCard 779S 4G AC779S NTGR779ABB Unite Express AirCard 810 AirCard 810S Explorer 2 AirCard 797S AC797S

Replaces Part Numbers

W-8 308-10004-01 W-7b

Technical Specifications

Voltage3.7V
Amp Hours2400mAh
Capacity2400mAh
Rate8.88Wh
Net Weight55g /1.94 oz
Gross Weight105g /3.70 oz
Approximate Weight105g /3.70 oz
Dimension 77.45 x 54.24 x 6.30mm

Product Highlights

  • Brand: AT&T
  • Manufacturer: CS
  • Series: X-Longer
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My AirCard 779S keeps dropping everyone off the WiFi mid-session even though the battery shows half charge — is the battery dying?

Yes, a half-charge indicator doesn't mean the cell can still handle peak current. When the modem and WiFi radio both run at full draw — which happens with multiple connected clients or a weak cellular signal — a degraded cell sags below the BMS cutoff voltage and the hotspot shuts the output to protect the cell. Replace the battery and the sag disappears; the indicator was measuring remaining capacity, not delivery capability.

The 779S battery drains much faster than it used to even with just two devices connected — what causes that?

Check your signal bars. In a poor coverage area, the cellular radio cranks to maximum transmit power trying to hold a connection, drawing significantly more current than it does in strong signal conditions. That extra draw collapses apparent battery life fast. If signal is strong and drain is still heavy, the original cell has capacity-faded below its rated 2400mAh — a fresh cell at full rated capacity restores normal endurance.

Can I recover an AirCard 779S that won't turn on at all after weeks in a drawer?

Most of the time, yes. The cell has likely self-discharged below 3.0V, which is below the minimum voltage the device needs to boot — the BMS blocks startup to prevent damage. Plug the hotspot into a wall charger (not a laptop USB port, which may not source enough current) and leave it connected for at least 30 minutes without pressing the power button. If the LED doesn't respond at all after 45 minutes, the cell has gone below recoverable voltage and needs replacement.

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