I have read on other forums that there has been a rash of problems when owners use their key to pull back the rubber protective cap on the battery charging area. The metal key creates a spark, which kills the fuse. Never use a metal object to pull back the rubber flap.
In addition, Rad suggests plugging the charger into the battery first, then plug the charger in the wall. I am fairly confident everyone does the opposite with perfect results. But think about it, if the charger is plugged into the wall first, then you plug the charger into the battery, you do run the risk of creating a spark, which could kill the fuse. To be safe, follows Rad’s direction and plug the charger in the wall last.