first let me say i am glad to be part of this forum, have a project i am working on and need some help, i have taken a in dash car dvd player and installed it on my tailgating cart what i am using is a 12dvc regulated switching power supply which gives me 12 volts. the problem i have having is keeping memory to my radio presets, so i installed a battery which after time has to be charged so i got to thinking what if i could install some type of relay,which would allow the 12vdc regulated power supply to power the memory wire and once i cut off the system the 12vdc battery will kick in does this sound possible?