'05 alternator problem!

[Palmtree]

Went to start the truck today after it had been sitting for 28 days and the "check gauges" indicator light was on. The alternator gauge was dead, flat lined. All the lights and so on were fine. Desperate to get home - 650 kms- drove to the nearest town. By the time I arrived, my lights were dim and the truck was stalling. Luckily I was able to limp to a Safeway parking lot and fire up the Yamaha generator and hook up the battery charger, charging up the batteries to 66%. I started the truck and drove another 10 minutes until the gauge lit up again and the battery gauge had flat lined again. I hooked up my charger to the battery and left the generator running, suppling the battery with a charge as I continued down the highway. After an hour I pulled into a servivce station and shut off the truck to fuel up the generator, and when I restarted the truck, the battery charge indicator had come back to life. I figured it would crap out after another 10 minutes. But this time it didn't die...What the heck is this new intermittent electronic problem?? Has anyone else experienced this? Is it a relay or what? Any ideas??