Casablanca Car

Basically two days ago I put in a subwoofer and Amp in to my truck and I found a couple hours later that my battery was dead. It had no power at all. I was able to get a jump and it started right up. I went and had the battery tested and it said that it still holds a full charge, so I put it on a charger for over 8 hours, and once I put it back in to my truck it still wouldn't turn over the engine. There was some power, it turned on some lights. I did disconnect every extra add-on accessory that I added and it still wont start. I was able to get it jumped and it started right up. So I'm wondering, did I short circuit my alternator when I put in my amp and sub, or is there something else? I've checked around and all the connections seem pretty good. I've cleaned them up to make sure that wasn't it, and it still wasn't. Does anybody what I can do or where I can start?
The battery is within 1 year old