JF here thought I'd just chime in here the battery is perfectly safe right up to 160 degrees Centigrade we had it made that way and its costs more than other batteries. The case of the mojo when it's charging has to shed about 1. 7 watts of heat it can only do that by radiating it away or convecting it away. If it's in a warm environment or it can't covect its heat away it's temperature will rise until there is a sufficient temperature differential to shed its heat. It's perfectly safe we have three indepentdant thermal temperature safety shut down method in mojo so please don't worry we know what we are doing. Remember a really hot cup of tea is usually only about 60 degrees C.