He was charging it in the case which is a no no. I have used those types of battery boxes in the past with no issues. He claims the batteries touched in the case and shorted. Not sure of that. I am thinking the case foam acted as a blanket and the batteries over heated. Then a possible bad solder joint which could have covered up the vents around the positive button and kaboom. The slingshot battery boxes work great. Put all the batteries in the same way so the end battery bar tabs cannot touch and you should be fine. I always run my batteries for 6-7 min a time and then put them in the case. The latest 3600+mah batteries self discharge pretty hard so you always want to store them with some charge on them. Discharge them just prior to charging.