ESC 4/3S

If I have a brushless DC motor connected to a suitable ESC that can take up to 15V input does that mean I need a 4S battery (14.8V), or will a 3S battery (11.1V) be OK?

I guess what I am getting at here is, is there some electronics in the ESC that will step up the input voltage as required if I use a lower voltage battery?



No the voltage will not be "stepped up". The ESC will probably work at a lower voltage but will not be able to give the rated current. So it's best to use a 4S battery if you want to use it at it's rated current.