NinerBikes, the percentage state of charge can vary by battery brand, manufacturer and type. Generally speaking, 12.4 volts is more than 30% discharged for our RedTops (and 34M BlueTop) and more than 40% discharged for our YellowTops and BlueTops (except the 34M).
BFL13, if batteries have become sulfated, our engineers have indicated that cycling them down to about 11.5 volts and fully-recharging them at 10 amps two to three times can sometimes help break up some of that sulfation and restore some performance. I should point out that batteries resting between 10.0 and 11.0 volts tend to be more likely to have a bad cell, as the math typically suggest about 2.1 volts per cell. Take one cell away from a 12-volt battery and you drop into that 10.0-11.0 range. That's not to say that a good battery can't be discharged into that range and recovered, but that batteries that tend to settle into that range after charging is attempted usually need to be recycled.
MEXICOWANDERER, you pretty much hit the nail on the head...if I'm reading your post correctly. For RV applications, the amount of reserve capacity remaining after a battery has been cycled dozens or even hundreds of times is what often matters most, although short of running such a test in one of our labs, most folks won't know until they hit that 300th cycle (if they get there at all). Generally speaking, the shallower the discharge cycle, the longer a battery will last in a given application. In the examples you cited, the battery cycled to 80% DOD will probably not be able to be cycled as many times as the same battery that is only cycled to 60% DOD. What capacity the OEMs expect probably depends on the OEM and whether that refers to the battery manufacturer or the RV manufacturer. This is a chart we use quite often to illustrate the difference between the cycle life of our batteries versus traditional flooded products (note the identical group size comparison).
Jim McIlvaine
eCare Manager, OPTIMA Batteries
www.pinterest.com/optimabatteries
