1997 Ford Ranger ELECTRICAL FAILURE

I was driving down the road and all of a sudden my lights cut out and all power was lost to the vehicle leaving me and my truck dead on the side of the road, yet the battery had plenty of juice. I do not think it was the alternator but I cannot think of what it could possibly be, seems like theres a false connection somewhere but I dont know where. Battery cable are tight and complete to the starter and sarting celanoid.