C210 PLT HAD A GENERATOR FAILURE AT DUSK AT ZOA CLASS E. THE PLT NOTIFIED THE ZOA RADAR CTLR WHO DECLARED AN EMER FOR THE PLT AND REQUESTED SEARCH AND RESCUE TO INSURE PLT'S SAFE ARR.

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ENRTE TO NAPA ON AN IFR FLT PLAN IN VMC; THE ALTERNATOR FAILED. I NOTIFIED ATC OF THE PROB AND CANCELLED IFR. THE CTLR ALLOWED ME TO TURN OFF THE XPONDER; MAINTAIN VFR ALTS; AND KEEP HIM INFORMED OF MY ALT. NIGHTFALL WAS EMINENT AND MIGHT LIMIT THE CHOICES OF ARPTS WITH APPROPRIATE RWYS AND MAINT FACILITIES. RATHER THAN TURNING BACK TO RED BLUFF OR REDDING; OR DIVERTING TO SACRAMENTO (ONLY 10 MINS CLOSER THAN NAPA); I CHOSE TO PROCEED TO NAPA; WITH AN ETE OF 40 MINS. UPON HDOF TO THE ZOA CTLR; I NO LONGER HAD ENOUGH BATTERY PWR TO XMIT A REPLY THAT COULD BE HEARD. I THEN SHUT DOWN THE RADIO AND CONTINUED TO NAPA USING A HANDHELD NAV/COM TO GUIDE ME ON A BEARING TO SGD VOR. I LANDED WITHOUT INCIDENT AFTER SELF-ANNOUNCING ON CTAF (NO OTHER ACFT WERE RPTING IN THE AREA). 10 MINS LATER SEARCH AND RESCUE ACFT AND VEHICLES ARRIVED AND I NOTIFIED THEM BY HANDHELD THAT I WAS DOWN AND SAFE. BASED ON PREVIOUS EXPERIENCE IN A T210; I THOUGHT I WOULD HAVE 1 HR OF BATTERY PWR; BUT THE BATTERY LASTED ONLY 30 MINS IN THIS PLANE. MY CHOICE TO PROCEED TO NAPA; EVEN THOUGH IT WOULD ENTAIL A NIGHT LNDG; WAS INFLUENCED BY AVAILABILITY OF MAINT FACILITIES; LIKELIHOOD OF FBO ATTENDANCE; AND RWY LIGHTS; BUT ALSO DISTANCE FROM MY DEST. THE FIRST OAK CTLR HAD SAID HE COULD FOLLOW ME AS A PRIMARY TARGET; BUT I DON'T KNOW IF THE SECOND CTLR HAD RADAR COVERAGE DOWN TO ARPT LEVEL. OF COURSE; LNDG WITHOUT LIGHTS WAS NOT OPTIMAL; ESPECIALLY WHEN THE TWR WAS NOT OPEN TO NOTIFY OTHER PLTS IN THE AREA. IN RETROSPECT; I BELIEVE THAT DIVERTING TO RED BLUFF OR SACRAMENTO WERE NOT ANY BETTER CHOICES SINCE RED BLUFF IS UNATTENDED AT NIGHT AND SACRAMENTO INTL WAS ONLY A FEW MINS CLOSER AND HAS SIGNIFICANT TURBOJET TFC. TURNING BACK TO REDDING; HOWEVER; WOULD HAVE ALLOWED A DUSK LNDG WITH A FUNCTIONAL RADIO AT AN ARPT WITH MAINT FACILITIES AND RENTAL CARS. THE LONGER DRIVE FROM REDDING WOULD HAVE BEEN OFFSET BY A SAFER ARR.