Greetings and thanks for any help. Have searched site but didnt find answer so here goes. 1966 Cherokee 140. Bought new headphones and was testing along with other issues. Had master switch on for about an hour and seems liked drained battery. Not dead but radios started blinking, etc. Is that normal or do I have a weak battery? Does blinking indicate low battery? Finally what is best way to charge up. New to aviation so want to be sure before I just hook up to a charger. Thanks for any help!