c00lduke

I was having my battery tested the other day at Advanced Auto parts and it was releasing what seemed to be an awfull sulfer smell. The smell seemed to be hissing out of the 2 vents on top. Even after I brought it home 10 minutes later it was still hissing while sitting on my grage floor. I wasnt sure if this was normal or by any chance would explain why symtops I've having with it never seeming to put enough power how to start the car. Any ideas would be great.