When doing a load test on your RV battery, you are not interested in loading it like you would for testing a starting battery. On my boat, I load test my "house" batteries (I have 2 huge house batteries) by drawing about 7-10 amps and noting the battery voltage under that amount of load. My 12V refrigerator draws about 5 amps, so when it kicks on I can turn on a few lights, at about 1 amp per light, and then check the battery voltage. There IS a way to check the individual cells on your batteries. You can do this with a hydrometer. Each properly charged cell should have the same "specific gravity." If a cell is not properly charged or if it is "weak" it will have a significantly different specific gravity. I don't have the numbers handy and don't remember them, but I'm sure they could be looked up online. The hydrometer you need to do this is calibrated for specific gravity, not the ones with the floating balls.
Gary and Pat Harkins
Dodge 3500, 2011 CF305SKP