Because the car charger is generally used at home, the manufacturer considers the use of safety issues are to limit the charging current at about 10 amPs, so that the home electricity is safer, there is no need to change the main switch.
Since the general household 220V AC socket is 10A and 16A, for safety reasons, the charging current of slow charge is generally less than 10A, according to the standard calculation of 10A, the maximum charging power of slow charge is about P=UI=220V*10A=2.2KW. Since 16.25KW is much larger than 2.2KW, it can be found that fast charge is much, much faster than slow charge.