Going to buy a charger and saw the 4amp ID. About 15-20$ cheaper then the 6 amp. It says the ID does the cell count, the mah, based on what buttons you need to push, but did anyone saw it fail? I don't want to like pressure Traxxas but I know technology sometimes goes wrong and I definitely do not want a fire. Also, is it really worth the 20$ less than on the 6amp? Thanks!