C172 PLT HAD GENERATOR FAILURE.

Narrative

NEWLY PURCHASED ACFT; RETURNING HOME FROM PLACE OF PURCHASE; 'VOLTS' LIGHT CAME ON. DUE TO LACK OF EXPERIENCE IN ACFT (.6 DEMO FLT; .6 CHKOUT) IT TOOK ME SEVERAL MINS TO SORT THINGS OUT. I ELECTED TO LAND AT DBQ FOR MAINT; BUT REALIZED ABOUT 20 MI OUT THAT BATTERY VOLTAGE WAS DROPPING AT A RATE SUCH THAT MY RADIO MIGHT QUIT; SO I DECLARED AN EMER; AND IN FACT THE RADIO DID QUIT ABOUT 10 MI OUT; EVEN THOUGH ALL NON-ESSENTIAL ELECTRICAL EQUIP HAD BEEN SECURED EARLIER. HAD I BEEN MORE 'UP TO SPD' ON THE C172 ELECTRICAL SYS I THINK I COULD HAVE IDENTED THE PROB (ALTERNATOR FAILURE) EARLIER. I ALSO COULD HAVE BETTER ESTIMATED MY REMAINING BATTERY PWR IN MINS AND COULD HAVE CHOSEN A DIVERT FIELD WITHIN RANGE OF MY REMAINING BATTERY LIFE. THE BULK OF MY FLT TIME IS PART 121 AIRLINE AND MY RECENT GA EXPERIENCE HAS BEEN 6-8 HRS PER YR. THIS WAS ALSO A FACTOR. ALSO; I USED VALUABLE TIME STRUGGLING WITH THE GPS IN LOCATING A SUITABLE ARPT BECAUSE THE GPS WAS NEW TO ME. BOTTOM LINE; I WAS ABLE TO COMPENSATE FOR MY MINIMUM FAMILIARITY WITH THE ACFT WITH MY CONSIDERABLE AVIATION EXPERIENCE. I THINK THAT SUCH A MINIMAL CHKOUT COMBINED WITH A LOW-TIME PLT MIGHT HAVE HAD A LESS SATISFACTORY CONCLUSION.