The other day my stereo flicked on all by it's self in my truck and I can only assume that that is what killed my battery. The next day I asked someone to jump me and after we had my truck hooked up for a while I tried to start my truck, but it won't even turnover but my battery gauge read that my battery was were it should be and was fully charged, but my truck didn't make a sound when I tried to start it which is normal for a dead battery, but all my lights on my dash board were on and I could read the power gauge for my battery. Are there any suggestions for my truck?

Just in case... my truck is a model C1500 1990 longbed

 

Just a guess, but did you pull the battery cables and check for corrosion? My "new to me" 3500 had a lot of corrosion on the + side cable at the battery bolt. All I got the other morning was a "click", then nothing (as you described). I cleaned it off and applied some corrosion inhibitor. Has worked well since.