M20P SUFFERS TEMPORARY TOTAL ELECTRICAL FAILURE ON IFR FLIGHT. POWER IS RESTORED DURING RETURN TO DEPARTURE AIRPORT.

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I WAS ON AN IFR FILED FLT FROM ZZZ1 TO ZZZ. AFTER GETTING TO 6000 FT (FILED) AND ON COURSE; ZZZ1-ZZZ; I SAW THE BATTERY FLASHING ON THE MONITOR AND THE LO/AMP FLASHING. CHKED THE AMMETER. IT WAS DISCHARGING 11 AMPS AND SHOWING VOLTS 12V. I HAVE 2 INDEPENDENT 24V BATTERIES. SWITCHED TO THE SECOND BATTERY AND IT SHOWED THE SAME. AT THAT MOMENT; I DECIDED TO CALL ATC AND GET A VECTOR BACK TO ZZZ1. BEFORE I COULD PUSH THE BUTTON; I LOST ALL ELECTRICAL PWR (NO RADIOS). I REVERSED COURSE 180 DEGS AND HEADED BACK TO ZZZ1. BEING I WAS ON AN IFR FLT; I KNEW I HAD TO SOMEHOW CONTACT ATC. I CHANGED MY XPONDER TO 7700 DECLARING AN EMER. PICKED UP ATC AND ADVISED THEM OF MY SIT. THEY HAD ME IDENT AND ASSIGNED ME A VECTOR TO ZZZ1. I KEPT SWITCHING BACK AND FORTH BTWN BATTERIES TO SEE IF ONE WOULD COME BACK ON. MY #2 BATTERY CAME BACK ON; RESTORING ALL ELECTRICAL PWR. RETURNED TO ZZZ1 WITH ALL RADIOS WORKING. THE PLANE IS IN THE MAINT SHOP BEING CHKED OUT NOW (PROBABLY ALTERNATOR?). THE REASON I'M RPTING THIS IS BECAUSE I DECLARED AN EMER (7700) AND ASKED FOR ASSISTANCE FROM ATC. NO ONE ASKED ME TO FILE A RPT.