This is gonna take a minute. I have a 08 trailblazer, sometimes it will start other time not. Alternator is charging good. About 14 v. Battery acts odd. It is good at 12.8. It will drop all the way to 10v and still start. Then, out of the blue when I try to start it I turn the key and everything goes out. Nothing works. I can't even remove the key. Short of going to the dealership I'm not sure what to check next. Help.

 

Check your wires on your starter. The positive wire for the battery may be loose and causing it to not start and not have power.

 

Also check for corrosion on your battery terminals on both ends of the cables.

 

I recently had a problem with a battery from battery outfitters 1 month after purchase I started having trouble like you are saying it turned out the battery was dying another new battery this time from Walmart fixed it