So, my car battery died 4 months ago while it was unused in my garage during the summer (interior dome light left on for months). I went to jump start it this morning, ran it 20km ( 30 minutes ) to work and after turning it off, the battery is 100% DEAD.
I can't even engage the door locks it's so dead. It appears that the alternator just isn't charging the battery at all.
Is the battery likely well and truly dead? If so, What killed it? Was it because it was lying dead for such a long time? Or would that make any difference?
I'm going to try charge it overnight. There are a few stores that do battery tests and will even charge a battery overnight for you (they want to sell you a new battery). I can try that, but I'd be curious as to the cause of this failure to charge so I can avoid similar situations in the future.