OK ... I give up.
I'm usually pretty good at hacking around on the Internet, but this time I guess I didn't have enough cups of java: Where are you guys reading on the PowerMax link above that some of their units have PFC??
What I did notice however, is that the 55 amp PM3-55-MBA model, with it's maximum continuous power of 780 watts at >85% efficiency, just might be able to be fully powered from a little Honda 1000i generator. Wouldn't that be a sweet combination -> a 55 amp multi-stage charger being powered via the smallest Honda inverter generator!