I have another question about battery usage. I have a 21 rpod 196. I have two universal 12 volt 100amp batteries on board and for some reason overnight they go down to 50-60% and I have to charge each day. I am using the frig, the heater, and hot water all on gas. I know the water pump is going to drain the batteries some but this seems to be excessive. I have a friend that has only one of the 100amp batteries on his older 2019 rpod and he seems to be able to go for 3-4 days before charging using the same things. The inverter is turned off. We rarely use the fan in the bathroom. The hot water heater's electrical switch is turned off in the heater bay. Any suggestions or just validation that his should not be happening ? Thanks Hunter

You are correct, that is excessive usage.  Hopefully you have a voltmeter or multi-tester to check battery voltage.  First, make certain the electrolyte levels in the cells are full.  If low add distilled water until you get to the full mark.  Second, check voltage, each battery when fully charged at rest should read 12.72v or slightly higher.  If not run a trickle charge on each low battery, 2 amps is a good way to go - let it run for 24-36 hours to slowly charge battery.  After that let is set for 3-4 hours before checking voltage-again after charging it should read 100% or 12.72 volts.  Let it set for a day and check again, it should read about the same, if it is a lot less than it is a good indicator the battery has been hurt in the past and won't hold a charge.

I just replaced one of my 12v group size 24 Interstate deep cycle batteries last October; it was 3 months shy of turning 11 years old.  Maintenance is key to longevity and also not to run it below 60% S.O.C. or 12.2v before recharging.  My other 12v will turn 11 years old April 2022.  They will last with proper maintenance.  This is in northern Michigan.  When boondocking in colder weather (40's at night with the furnace running a lot) we expect 3 days before switching batteries.  As you do we also run fridge, furnace, hot water all on propane.

With your multimeter you could test to see if they will hold a charge.  Check electrolyte levels, fill with distilled water only, if low.  Give each a 24 hour 2 amp trickle charge and disconnect from the charger.  Let sit for 4-6 hours and take a reading.  You should get something between 12.72 (fully charged) to 13.3volts or so.  Take another reading a day later and then 2 days later.  The drop in voltage should be minimal. 

In northern Michigan where I am the 12volt batteries were charged November 1, 2020.  Since then they have been directly sitting on concrete in a unheated garage.  Temps for the last few days have risen to about -7C,  yesterday the temps never got above -14C.

I just checked voltage for both batteries, the oldest one (will be 11 years old in April 2022) read 12.52v the other one read higher and it has now been nearly 10 weeks since they were charged.  After a couple days the voltage shouldn't vary by more than 0.02 volts at the most, if so they have probably been hurt.  As advised above, go to an auto parts store and get a load test performed.

Not quite. AGM batteries are still lead-acid. It is just that the electrolyte (acid) is absorbed into glass mats which are between the lead plates, thus AGM. They do take a little different charging profile from flooded lead-acid batteries though. One charger I have as settings for flooded, AGM, and Gel batteries. All these are lead-acid.

https://mechanics.stackexchange.com/questions/44197/what-is-surface-charge-and-how-does-it-affect-battery-testing - https://mechanics.stackexchange.com/questions/44197/what-is-surface-charge-and-how-does-it-affect-battery-testing

Note that with AGM batteries, stratification is not an issue.

I recently switched out the battery box but that is a whole different subject.