Last night I had an alternator failure in a 172RG flying from Nantucket to Republic (Farmingdale) in New York. Being over the water at night, it was not the ideal place to lose an alternator, but the weather was good VFR and the moon was up, so I wasn't overly concerned. I immediately put the landing gear down so I wouldn't have to pump it later on, and shut everything down so I could have some power for landing. I put the sectional and flashlight to good work and was able to track the Connecticut shoreline to the north shore of Long Island. I soon realized that the tower would be closed by the time I got to Republic, and wasn't sure I'd have enough battery power to turn the runway lights on myself. I pulled out my handheld transceiver and tested it out by trying to turn the lights on at an uncontrolled airport I was flying nearby. Nothing. The handheld just wasn't strong enough. About 30 minutes from Republic I tried to raise New York Approach on the handheld and see if they could help get the lights on. The controller was very helpful and we worked out a few options, including getting another plane to turn them on for me. Getting closer, I picked up the automated weather on my iPhone to determine the runway in use. Turning final I switched the power back on to verify the gear was still down and locked and to flip on the landing light. We made an uneventful, flaps up landing (in case we had to go around and didn't have power to raise the flaps).
Here are the edited tapes from approach and Republic traffic at the end. You can't hear me talking to NY because the handheld was too weak, but it picks us up coming into Republic.