What kind of batteries to get?

Get the biggest 2*12V or 2*6V that will fit in there and won't overload the tongue beyond what it's rated. Just make sure it says "deep cycle". Most likely you'll end up with 200-220 AH total bank capacity.

Few misconceptions here by the OP.

You (probably) don't have a propane heater. People install those themselves, and love it, but most RVs come from the factory with a furnace - not heater. It draws a lot of 12V, and a lot of propane. And it makes a terrible noise, waking you up every time it cycles in the night.

Your fridge will (probably) run on propane all the time, except for when on hookups, and while on propane, it will also need 12V power for thermostat - quite a lot. More than you'll need for lights and radio/CD. OTH, propane consumption is not too bad - 6 cu.ft fridge on 77F day needs about 1.2 lbs daily.

Running propane fridge while on the road is debatable. It is generally not recommended. But people do this, with no consequences that I know of. These fridges are shallow front to back, they lose most cold air when you open it. But if you keep the door closed, it will hold the temperature for a few hours, so there isn't much need to run it on the road.

FWIW: All batteries have a limited amount of discharge cycles before they die, and they die sooner if allowed to discharge deeper. The nice thing about solar is that batteries are not discharged as much or as deep meaning longer life. A good 3 stage built-in charger/converter will do the same. We have a friend who rarely lets his battery bank get below 12.4 volts and his batteries last 8 years (12.6 is fully charged, 12.2 is 50% discharged).

tjcooper wrote:
QUESTION: I read the 10 page thread review on "one 12volt vs two 6volt battery" section from the 2008-2011 time period. It appears to be a closed thread. From above I see there are like 100 threads on the 12volt parallel vs 6volt series debate. Can someone point me to a good "truly technical" discussion of deep cycle of the parallel vs serial debate?

I have a Ph.D. in physics and deal with NiMh and LiPo batteries on a daily basis. With those types of batteries it is always better to have the SERIES configuration over the PARALLEL type. I have no idea if the same properties hold for the Lead-Acid type. I want to understand any differences.

I think you've answered your own question:
Threads on here are not "truly technical" discussions.
A Ph.D. in physics knows that series is better.


I'm in the solar industry and build a lot of big battery systems. Standard practice in this industry is that one series string of cells is best. Use 2 strings if you really have too for some reason. And 3 strings is the absolute maximum if you want the batteries to even remotely charge and discharge evenly.

Most arguments for parallel 12v cells involve: they're cheaper at some big box store, I'm not strong enough to lift a big 6v, or something like that.

I read your post again, DO NOT use your battery to run the frig,use your propane side of the frig while traveling, the frig will kill a battery in no time. for your use ,just stop at wal mart buy two deep cycle batteries. and they,ll work just fine. p.s the frig will use very little propane.

QUESTION: I read the 10 page thread review on "one 12volt vs two 6volt battery" section from the 2008-2011 time period. It appears to be a closed thread. From above I see there are like 100 threads on the 12volt parallel vs 6volt series debate. Can someone point me to a good "truly technical" discussion of deep cycle of the parallel vs serial debate?

I have a Ph.D. in physics and deal with NiMh and LiPo batteries on a daily basis. With those types of batteries it is always better to have the SERIES configuration over the PARALLEL type. I have no idea if the same properties hold for the Lead-Acid type. I want to understand any differences.

My two 6volt 220 AH system are showing strong signs of dying after 4 years of 3 times per year use with a solar charger installed. I am trying to decide whether is better to convert to two parallel for cheaper batteries and replace them more often, or stay with very expensive 6 volts.

I just saw that Amazon has T-106 Trojans for $156 and I can get free local pickup here in Silicon Valley. Is it typical to find local battery dealers who will discount the expensive batteries and also offer free local pickup? Thanks.
tjcooper

Two 6v GC2 golf cart batteries will be the most bang for the buck in a true deep cycle battery. My two 6V's from Sam's club were $190 out the door including the core charges. Circa 2012.

You might want to update the converter to a 3 stage charged system or better. Most stock converter/ chargers just boil the batteries to death.

Here is some good reading.
http://www.gonewiththewynns.com/RV-Smart-Converter-Charger

I went with the Optima Batteries 8027-127 D27M BlueTop Starting and Deep Cycle Marine Battery. I got tired of maintaining the 6 volt batteries. They cost a lot, but work very well.

We almost always camp with electricity, we can run a day or so on the battery if we need to but it is the exception. Hence we have a single deep cycle battery.

The main use of the battery is to keep the various phantom loads going while towing and the water pump running when stopping for breaks.

Batteries Plus carries a great selection of Deep Cycle Batteries and their prices were reasonable as any ...