Vampires and multimeters

Originally posted by spydie Consider using two 12v batteries in parallel which doubles your camping time. Doubles your amp hours. Two six volt batteries in series only doubles your voltage. No gain in amp hours. As an alternative you are going to have track down the culprit draw

Two 12V batteries are not necessarily any better. Most 6V batteries used are 220AH GC2s. Together they provide 12V at 220AH. The usual 12V battery is a Gp24 with about 86AH so a pair would provide 12V at 172AH, which is significantly less than the two GC2s. That said it still seems the OP has a significant constant load on his batteries. The only way to confirm this is to put the ammeter in series right at the battery terminal or use a clamp on ammeter around all wires right at the battery terminal. This means all connections including the load distribution (fuse) panel, solar panels, breakaway brakes, and power tongue jack if applicable. If a significant load is confirmed the isolation and troubleshooting process can begin. If no significant load is found it points to the battery or charging system.

Originally posted by GLBCamper But when camping, the only thing I am adding is running the fridge (mine does not have 12v function), running the water pump for maybe a total of 5 minutes and turning on one LED light for maybe a total of 10 minutes and I will go from 12.6 to 12.0 by the next morning. None of those things seem like a HUGE draw. So I guess that narrows it down a bit, but I'm not sure what to do next.

I should add that it might be time to take a closer look at your batteries.  Have a local battery house measure and evaluate the specific gravity for starters.  And if you can access each cell, measure each cell as the battery is being charged.... and then discharged in camping mode.  They should all be the same voltage.  A low or high cell at any point would be very suspect.  

Brakes are good. I check them regularly with a laser thermometer. Hubs and brakes run low 100's while towing, even on VERY hot days. 

Also, you never stated what the assumed battery capacity is.  We are assuming you are using a pair of 6V golf cart batteries, which would get you 12V at >200AH.  What are you actually using and exactly how were these batteries tested for capacity?  It is not possible to do accurately in any short term test.  You can infer capacity using a cold cranking amp tester but the most reliable way is simply to discharge at a constant known current for a known period of time to a known state of charge and do the math.  Does the AH consumed (discharge current X discharge hours) roughly equal the capacity removed based (starting % charge - ending % charge X rated battery capacity).