The Diehl alternator setup on my plane is the old single phase system, and is a permanent magnet ring mounted to the flywheel, with a bunch of coils surrounding it (bolted to the case). The regulator has two AC inputs from the coils, and one output to the battery. I'm pretty sure the coils and magnets are from an Onan generator. It delivers an amazingly steady 14.5V output, and charges anywhere north of 1500 rpms. I have a couple of $1 50A Schottkey diodes that manage the backup battery charging and isolation from the main system. That backup battery is constantly being charged by the alternator (as is the main battery), but a drain on the main side won't hurt the backup side. They are rated at a current that will act as a fuse in case of a short in the main system, isolating the backup from the main. I'm quite happy with the failsafe nature of the system, and the price was right...
Mark Langford ML at N56ML.com http://www.n56ml.com
