I have a PC680, 2.5 years old.
I left my master on.
I used a sears 10/2 amp charger, took 2 hrs at about 4--6 amps indicated to get enough in it to start the engine. Then flew for 1.5 hrs. Alternator started out charging at about 25 amps, quickly dropped to 16 amps, then slowly over time, dropped to the normal 2 amps or so.
Battery seemed fine for about 2 weeks. Now, most of the time, it won't accept any charge from the aircraft alternator, and the alternator voltage floats high (like 15.3 v or more) but shows slight battery discharge. Sometimes, by putting some load on it, like turning strobe lights on, the battery will then accept the charge, the alternator drops to normal 14.7 or so, and battery charges at 16A for awhile, then slowly drops to normal 2A or so.
But later, the battery is down to 10 volts again.
it is a plane-power alternator.
I just ordered a new PC680