In May 2013 I bought a deep cycle battery ( I think group 24, will confirm tonight when I see it. Powers lights and GPS only for a few hours in evenibev, maybe 15 nights a season, 1 overnight per season. I plug into trickle charger on Wed. or Thurs. Evening for weekend use. Kepple trickle charger in it over winter, turn it in for 1-2 nights once a month. This week, plugged in 3 - 4 days, never got to " charged" light on , always charging. At a friend's house now in regular charger for overnight, showing 13.3 volts now, is it likely to come back next time with trickle charger? What is normal life span?