I had the same question about charging the lithium ion battery in my bb 9930 so i called blackberry tech support and they looked into it and said the initial charge should be 4 hrs! And after that 2hrs charging. They told me overcharging the battery, like charging it for 12 , 16 or 24 hrs will lead to damage in the battery! They said you dont need to let battery die all the way between charges either. This is straight from blackberry tech support 1877 552 5532 Good luck !