Welcome to the forum, happy holidays. 12.5 volts is not good output from the charging system. I like to see well over 13 volts at idle, all electricals turned on. Anything under 13 I consider a weak charging system.
If the battery is down, take it off and get it charged, don't use the alternator. I can't rule out a battery drain, normal may be around.030ma, no where close to 1/2 amp.
Sunday, December 20th, 2009 AT 2:10 PM