A C172 AFTER LNDG AND TURNING OFF RWY EXPERIENCED COMPLETE ELECTRICAL FAILURE. RPTR TAXIED; CROSSED RWY ALL WITHOUT CTL.

Narrative

I LANDED AT ZZZ; US; IN MY C172. AFTER TAXIING OFF RWY 1 ONTO TXWY G; I SUFFERED A COMPLETE ELECTRICAL PWR FAILURE. MY RADIOS FAILED. (THEY HAD BEEN WORKING FINE BEFORE.) WHEN THIS HAPPENED; I TURNED THE AIRPLANE TOWARDS THE TWR AND WAGGLED MY CTLS; EXPECTING TO SEE A LIGHT. BUT; ERROR #1; I DID NOT WAIT VERY LONG AND; ERROR #2; BEGAN TAXIING DOWN THE TXWY. (I AM FAIRLY SURE I WAS CLRED TO DO THIS BEFORE THE RADIO FAILURE; BUT CANNOT REMEMBER.) THEN I CAME TO RWY 6; WHERE I STOPPED. I COULD SEE MY DEST FBO DIRECTLY ACROSS THE RWY. ALSO; I COULD SEE THAT THE RWY WAS CLR AND THAT NO ONE WAS LNDG ON IT; IT WAS VFR; BUT ERROR #3; I TREATED THE SIT AS SIMILAR TO MY HOME; UNCTLED ARPT. SINCE I COULD SEE THERE WAS NO CONFLICTING TFC; I CROSSED THE RWY. I REALIZED IMMEDIATELY THAT I SHOULD NOT HAVE; BUT; WITH NO COMS I SWITCHED TO THE MODE I USED AT MY HOME; UNCTLED ARPT; WHICH WAS SAFE; BUT IMPROPER IN THE CIRCUMSTANCES. SHORTLY THEREAFTER I REGAINED ELECTRIC PWR AND RE-ESTABLISHED RADIO COMS. (THE PROB WAS CAUSED BY A DEFECTIVE BATTERY.) THE CRITICAL FAILING WAS MY ADOPTING THE MODE I NORMALLY USE IN A NO RADIO ENVIRONMENT WHEN I SHOULD NOT HAVE. ANOTHER FAILURE WAS TO GIVE THE TWR TOO LITTLE TIME TO FIGURE OUT THAT I NO LONGER HAD ELECTRIC PWR; AND HAD NO RADIO COMS.