A few days ago my 2008 5.7 liter Commander would not start. I searched through the forums and found this site, was impressed and joined. I jump started the truck to get it to a local Auto Parts store to perform a diagnostic test to check the battery, regulator , and alternator. The test passed with no problems found. The battery tested good under a load. Frustrated, I returned home and disconnected the battery terminals and charged the battery. When finished I had a voltage of 12.8vdc. I then let the battery rest un-connected for 24 hours and only read 10.3 vdc. This proved even though the battery tested good, I had bad cell in the battery. A good battery should hold a charge for months if fully charged and not connected.(not stored on concrete floors). The end result is don't forget to let a battery "rest" after charging with no drain and recheck in a day or two to see if the voltage drops. The specific gravity could not be checked on a sealed battery, and this simple check could save you some bucks! By the way I went to a different Auto parts store and got a new battery.