I believe this is in reference to your AGM battery not your wet cell. A deep cycle battery is alot different from the factory battery installed in the vehicle. A wet cell battery has a higher capacity and also higher internal resistance were as a deep cycle battery has a lower CA rating and a lower internal resistance. A deep cycle battery is not as good for starting a car but its better for your audio system. The reason your voltage is higher without a draw is because of the design of your battery, I don't want to explain the difference so just google it or read it at /www.realmofexcursion.com/forum/showthread.php?t=923 just a good place to read and make some of your own decisions whats best and why stuff works.