A BE55 lost both alternators in flight but the pilot was able to talk with ATC on a portable radio and land at an enroute airport.

Narrative

We were flying the second leg of a golf trip. We departed and were enroute when a sudden drop in system voltage was noted along with loss of both alternators. Flew for about 10 minutes trying to trouble shoot. As much electric was shut down as possible; but still losing voltage; now down to 16. Asked if we could turn off transponder; and approach said fine as we would be a primary target. Not wanting to travel further as we knew we would have to crank down gear at night; asked to land at a nearby airport. Approach said fine; but then we lost ability to transmit on radio. We could still hear approach. Asked to IDENT so put back on transponder; but they had no mode C on us; therefore did not know our altitude. Warned us of tower at 1;200 ft; but we were at 4;500. Controller was awesome! Finally got hand-held radio working and regained two way communication. Asked to fly around over airport while we got gear down. We were cleared to land by approach; and did so uneventfully. Had difficulty hearing tower. May have departed taxiway illegally at one point due to no lights and very bright surface lights. Tower toned down lights. They then guided us to the FBO. Should have had a better understanding of taxiways; and clearance; but just coming off of a no light; no flap landing with gear warning system blaring all the way down final due to electrical difficulties! Perhaps should have declared an emergency earlier with approach; but did not seem a true emergency.