PA24 PLT FLYING AT NIGHT ON AN IFR FLT PLAN DIVERTED AND MADE A PRECAUTIONARY LNDG DUE TO AN ELECTRICAL SYS PROB AND IMPENDING LOSS OF NAV AND COM EQUIP.

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DURING PREFLT OF MY ACFT; BATTERY WAS NOTED TO BE COMPLETELY DEAD; WITH MASTER SWITCH LEFT ON. JUMP START WAS OBTAINED FROM LCL FBO AND FLT WAS CONDUCTED TO ZZZ1 WITHOUT INCIDENT. THE GENERATOR FUNCTIONED WELL DURING THIS 1.5 HR FLT; WITH POSITIVE AMPERAGE INDICATION; AND NO PROBS WITH ELECTRICALLY-DRIVEN EQUIP. ACFT WAS PARKED AT ZZZ1 FOR ABOUT 4.5 HRS. UPON RETURN TO ACFT; IT WAS DISCOVERED THAT THE BATTERY HAD NOT CHARGED ENOUGH TO START THE ENG; ALTHOUGH LIGHTS AND FUEL PUMP WORKED NORMALLY; AND ANOTHER JUMP START WAS OBTAINED. ALL RADIOS THEN WORKED WELL. IFR CLRNC TO ZZZ2 WAS RECEIVED. THE AMMETER REGISTERED A SLIGHT DISCHARGE DURING TAXI; NORMAL FOR THIS ACFT -- GENERATORS DON'T PRODUCE MUCH PWR AT LOWER RPM. AFTER TKOF; HOWEVER; I NOTED THAT THE AMMETER CONTINUED TO SHOW DISCHARGE; AND FORTUNATELY DECIDED NOT TO IMMEDIATELY RETRACT MY ELECTRICALLY-OPERATED LNDG GEAR. I WAS HANDED OFF TO APCH CTL WHO CLRED ME DIRECT TO ZZZ2 AT 6000 FT. SHORTLY THEREAFTER (PERHAPS 5 MINS); AT 5000 FT; I CAME TO THE DECISION THAT THE ACFT WAS NOT CHARGING ITS BATTERY AND WAS LIKELY TO LOSE NAV AND RADIOS. I COMMUNICATED THE SITUATION TO APCH; WHO GAVE ME A VECTOR TO ZZZ3; WHICH BY THEN WAS THE CLOSEST AIRFIELD. I WAS INSTRUCTED TO DSND TO 2800 FT. AT THAT POINT; THE RADIOS SUDDENLY WENT DARK. MY HANDHELD GPS CONTINUED TO FUNCTION WELL; AND THIS; ALONG WITH THE VISIBLE AIRFIELD ROTATING BEACON; ENABLED ME TO QUICKLY FIND ZZZ3 AND DSND TO PATTERN ALT. AT THAT POINT; THE RWY LIGHTS CAME ON TO FULL INTENSITY; WITH REILS FLASHING AT THE THRESHOLD FOR RWY 28. I LOOKED FOR LIGHT GUN SIGNALS; BUT DID NOT KNOW WHERE THE TWR WAS LOCATED AND FOUND LIGHTS ON THE GND AND THE ROTATING BEACON TO BE DISTRACTING. I CONCENTRATED ON FLYING THE AIRPLANE; FLEW A STANDARD L PATTERN TO RWY 28; AND LANDED UNEVENTFULLY. I CALLED THE TWR TO THANK THE CTLR AND CANCEL MY FLT PLAN. HUMAN FACTORS: ANALYZING THE SITUATION IN RETROSPECT; I FEEL THAT I SHOULD HAVE NOTED THE UNUSUAL LACK OF AMMETER CHARGING DURING THE RUN-UP; AND SHOULD NOT HAVE TAKEN OFF. BARRING THAT; I SHOULD HAVE RETURNED IMMEDIATELY TO LAND WHEN I MADE THE DECISION NOT TO RETRACT THE LNDG GEAR. DURING CLBOUT; I WAS CONCERNED ABOUT THE SITUATION; BUT BRIEFLY ALLOWED MYSELF TO BE REASSURED BY THE BRIGHTLY LIT DISPLAY OF THE GARMIN 430 AND THE CLARITY OF RADIO RECEPTION AND COM. I HATE TO THINK IT; BUT THERE WAS PROBABLY AN ELEMENT OF 'GET-THERE-ITIS' INVOLVED. OUR 15 YR OLD SON WAS HOME ALONE AND BOTH MY WIFE AND MYSELF WERE FEELING THE NEED TO GET BACK. FORTUNATELY; THE WX WAS EXCELLENT. FORTUNATELY; I FINALLY LISTENED TO MY INNER VOICE BEFORE ACTUALLY LOSING RADIOS COMPLETELY. THIS ENABLED THE CTLR TO ALERT THE TWR AT ZZZ3 WHICH MADE THINGS MUCH BETTER. DURING MY STUDENT TRAINING; MY INSTRUCTOR HAD ME LAND SEVERAL TIMES WITHOUT LNDG LIGHTS; AND I WAS THEREFORE CONFIDENT OF MY ABILITY TO DO THIS. I AM GRATEFUL TO HIM FOR THIS TRAINING. ANOTHER HUMAN FACTOR WAS THE PROB WITH LEAVING THE MASTER SWITCH 'ON' AFTER MY LAST FLT; THUS DRAINING THE BATTERY. I AM ALWAYS CAREFUL TO TURN IT OFF AND REMOVE THE KEY FROM THE IGNITION WITH MAGNETOS OFF WHEN I LEAVE THE PLANE; BUT SOMEHOW NEGLECTED TO DO THIS. CLRLY; I NEED TO GO THROUGH MY SHUTDOWN CHKLIST MORE METHODICALLY. GENERALLY; I LEAVE THE ROTATING BEACON SWITCH 'ON' TO ALERT ME TO THE MASTER SWITCH BEING ON; BUT THE BEACON SWITCH WAS 'OFF' AND THE BATTERY HAD DRAINED WITHOUT ME NOTICING IT. MECHANICAL FACTORS: I DO NOT YET KNOW FOR SURE WHY THE GENERATOR FAILED TO FUNCTION THAT NIGHT; WHEN IT WORKED SO WELL EARLIER IN THE DAY. THE HANDHELD GPS UNIT WAS ALSO A REASSURING ITEM THAT GAVE ME GREAT CONFIDENCE IN LOCATING THE ARPT. BECAUSE IT ALSO DISPLAYED EXTENDED RWY CTRLINES; I HAD NO DIFFICULTY POSITIONING THE ACFT QUICKLY FOR A STANDARD PATTERN APCH EVEN BEFORE THE RWY LIGHTS BRIGHTENED.