All you need for perfect regulation at 13.8 vdc is to connect two 12 v chevy batteries in series across the basic filter caps - via a 20 amp fuse - in a 961 or 962 power supply. The 24 v will be regulated down to 13.8 in exactly the same fashion as when you're running on ac power. (They must be chevy batts). 73 & fun, Roy K6XK/0