Went out to start my truck today, realized that I left the key on and the battery was dead. I took out the dead one and put in one that I had coincidentally been charging. I have no power. The dash lights, heater, radio etc. are not getting any juice. I am certain that the battery is fully charged. What could be the problem? I really need this issue to go away before a little road trip tomorrow, please help.

 

Did you check your fusible link connectors at the battery?

 

X2
I had the same issue on my 82. I spent 2 hours trying to figure out where things went wrong. Instead of starting at the battery I started elsewhere. 2 hours later I found the connection at one of the green plugs had come loose at the battery. Soddered it back up and I was good as new.

 

Figured it out. There was a ton of corrosion in one of the fusible link ends, sprayed some battery cleaner and she started right up.