As you can read from other posts I am in the hunt for a new battery.  The two I have now are identical Interstate 12v group size 24 deep cycles with the exception of one having a 12/2010 date on the battery and the other 04/2011.  The older one is the one that appears to be near the end of its useful life.

Charged it for 30 hours at 2 amps and let it rest for 4 hours.  The reading at this point was 12.51 volts.  After 8 hours it dropped to 12.29 volts.  One day later it now reads 12.22.

The other battery (4 months newer) was connected to the converter and was charging on our last trip, the last day being charged for just over 3 hours while we traveled home.  One day later I disconnected the ground cable.  It has now been 3 days since getting charged and it currently reads 12.75 volts, so all is good there.

It has been good and given great service.  The only difference between the two was on one of our first trips I decided to utilize the 12v function on the fridge by precooling it before leavinig.   After 6 hours I heard a beeping inside and then realized the battery's energy was depleted - how far down in voltage I do not know as I didn't have a voltmeter at the time.  Other than that they have had the same care and maintenance.