SMA PLT HAS COMPLETE ELECTRICAL FAILURE ON IFR FLT PLAN. DIVERTS TO NEARBY ARPT.

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I DEPARTED EEN; IFR TO BTV. UPON CLBOUT I WAS IN CLR WX. ASSIGNED ALT ON THE IFR FLT PLAN WAS 6000 FT. ONCE AT 6000 FT I ACTIVATED THE AUTOPLT'S ALT HOLD (INDICATED LOCKED IN). MOMENTS LATER I NOTICED THE PLANE HAD ENTERED A CLB AND THE AUTOPLT HAD DISENGAGED. I IMMEDIATELY RETURNED TO 6000 FT AND TRIED TO RE-ENGAGE THE ALT HOLD. IT WOULD NOT ENGAGE. I NOTICED BY THE DIMMING LED'S ON THE INST PANEL; THAT THE PLANE WAS RAPIDLY LOSING ALL ELECTRICAL PWR. I ATTEMPTED TO CONTACT ZBW ON COM #1 BUT REPEATEDLY RECEIVED NO REPLY. I THEN TRIED ON COM #2 AND AGAIN NO REPLY. BY NOW FUEL INDICATIONS HAD GRADUALLY LOWERED TO 1/10TH L TANK AND 1/4 R TANK. I SHUT OFF ALL NONESSENTIAL ELECTRICAL DEVICES AND ATTEMPTED TO LOWER THE LNDG GEAR. THE GEAR WOULD NOT COME DOWN. AS I WAS IN CLR WX AND AN ARPT WAS 8 MI NE OF MY LOCATION I CHOSE TO DEVIATE FROM MY FILED FLT PLAN AND LAND AT VSF. AFTER MANUALLY LOWERING THE LNDG GEAR I LANDED WITHOUT INCIDENT. I THEN IMMEDIATELY NOTIFIED THE BANGOR FLT SVC OF MY SIT (VIA TELEPHONE) AND ASKED THAT THEY NOTIFY ZBW AND TO HAVE MY IFR FLT PLAN CLOSED.