obviously it supplies power. i was under the impression that it takes a/c and converts to d/c for d/c chargers. but at the track i see guys using a charger that could be a/c or d/c using them even when there is power available at the track to just plug into. so i ask, if i use a generator and my chargers will use a/c power, is there any reason to invest in a power supply? are there any other benefits to using a power supply? what am i missing here?

Most chargers with an internal PSU cannot be used to the max specs. I have an old Duratrax charger which can charge 3A on its own PSU and 5A on an external PSU.

But yes, if you have AC chargers which can be used to the max (or within your needs) then there is no need for an external PSU. But an external PSU could be very handy for the supply of other equipment like tire warmers, Proxxon 12v multi tool, 12v LED light etc.

thanks that helps