Hi NJ!
I have two St Jude stimulators, they were implanted in June 2011. I received a letter from St Jude a month or so ago regarding battery overheating in certain models (mine being one of them). I have noticed that mine do get pretty hot when charging. My rep told me to charge more often since it would cut down the amount of time spent charging each time. It really does help. They told me that they would not do anything about it (replacing it) unless charging got painful. I am good with that since it is not hurting.

Sorry you need to have your battery changed out. Good luck with your surgery.
Nanc