Here's a possibly stupid question I'm a little unclear on. On most GA planes, does the electrical system run directly off the alternator in flight, or does it run off the battery and the alternator constantly keeps the battery charge at a certain level? I always understood it ran directly off the alternator, but I had an electrical failure in a 172 and the explanation the school gave me was that the connection on the battery was loose (it had happened before). Also, on the Piper ammeters (that show electrical load rather than rate of charge), what's the indication that an electrical failure is likely? Lower than normal load, or higher? The kind Cessna uses always seem a little easier for me to understand at first glance.