RE; Using a 230V AC to 13.8V DC in the USA
 

A normal storage battery (automotive) that I use as a standby is 13.8 Volts
as it is in the automobile. I also have a standby generator, but the
battery is the primary backup till the Genset starts. Anyway I have the
battery for a RCI Ranger 2950 which I use in the radio shack and another in
the mobile. 13.8 is GREAT

Whatever primary voltage (115 or 230) makes no difference, just whatever the
convertor requires.