how many batteries

[elmerfudd51]

put a deposit on a small jayco toy hauler (octane 222). will pick it up next week. will be mostly used in campgrounds but few times a year i go to nascar races for 3-4 days at a time. have a generator to run during day as necessary but concerned about keeping fridge and furnace running at nite.
how many batteries should i ask for? 1 or 2 12 volts or two 6 volt gc2 batteries?

[pnichols]

I bought our new RV batteries several weeks ago at a solar equipment dealer. Solar dealers are most likely to carry the true deep cycle batteries that you want in an RV.

[pianotuna]

Hi,

Measure the compartment.

An RV store would be the last place I'd go to purchase a battery.

red31 wrote:
What size battery(ies) will fit?

Is an RV store a good place to purchase battery(ies)?

[red31]

What size battery(ies) will fit?

Is an RV store a good place to purchase battery(ies)?

[pianotuna]

BFL the batteries will still sulfate if you only get to 90%. The ideal for me is to have enough solar to service enough capacity that the generator can be left behind.

[BFL13]

pnichols wrote:
BF,

As you know, having as large a battery capacity as one either can fit or can afford means one may have battery capacity so large that - all or most of the time - one uses and recharges only the "very top" of their battery capacity. This means that one's battery(ies) will last the longest time possible, all other things being considered.

Staying as shallow as possible on daily battery discharge cycles is a good thing. One can achieve this simultaneous with heavy daily use of battery energy if their overall battery capacity is large. Also in emergency situations (such as extended low sun-light conditions or being otherwise "stranded"), one may thank their lucky stars that their battery capacity was "larger than normally necessary".

IMHO one need only match daily charging capacity (be it solar or generator) to whatever the average daily battery discharge levels are ... NOT match daily charging capacity to around 50% of whatever battery capacity is installed if installed capacity is large.

Phil, you forgot that staying at the top end of the SOC band means it will take forever to do the recharge of the needed AH. Which is why you do 50-80s or 50-90s to keep generator time at something reasonable.

You can have too much battery so that when you get to 50% you only need to get back to 70% to be good for the AH, but if you stop there they will sulfate like crazy, and get big progressive capacity loss from successive incomplete cycles too. If you have an idea of your AH usage, you can get the bank sized right to do your 50-90s in a short time where the 40% of the capacity matches your usage.

[pnichols]

BF,

As you know, having as large a battery capacity as one either can fit or can afford means one may have battery capacity so large that - all or most of the time - one uses and recharges only the "very top" of their battery capacity. This means that one's battery(ies) will last the longest time possible, all other things being considered.

Staying as shallow as possible on daily battery discharge cycles is a good thing. One can achieve this simultaneous with heavy daily use of battery energy if their overall battery capacity is large. Also in emergency situations (such as extended low sun-light conditions or being otherwise "stranded"), one may thank their lucky stars that their battery capacity was "larger than normally necessary".

IMHO one need only match daily charging capacity (be it solar or generator) to whatever the average daily battery discharge levels are ... NOT match daily charging capacity to around 50% of whatever battery capacity is installed if installed capacity is large.

[pianotuna]

This is what is balanced and best for twin twelve volt batteries.



As it often doesn't cost a dime more to do this, I think it is worth the trouble.

[elmerfudd51]

thanks guys for all your help.

pickup the camper this thursday. will try to get two of the best 12 volts i can get from the dealer.

will be going to talladega in late october. was there once before but it was the spring race. only downside of trip is going thru atlanta, but going thru before rush hour should be tolerable.

[pianotuna]

I'd prefer to have zero generator time. That means going to a mid to large battery bank. The large bank doesn't necessarily mean 'extra' solar so long as there is enough to do equalization for a part timer and to replace the energy used each day for a full timer (plus something for recharging the bank). That, of course, depends on the end user. It all boils down to doing a proper energy audit. Then designing a system that works.

[BFL13]

RJsfishin wrote:
I think every off grid RV should have 2 batteries (200 AHs typical) 12v or 6v, don't matter, its still 200 AHs w/o getting all techie.

But between limited life span, and hauling dead weight around, batteries (like horses) eat hay. So my advice is don't have more batteries than you need, meaning, have just enuff to keep from discharging more than 50% each day.

Do have a means of charging those batteries in about 2 hrs generator run time each day,.....even if they don't get 100% charged. If you have 300 watts of solar, and can depend on sun every day, the batteries will take care of them selves, you don't have to even think about them.

Statements such as "You can't have too much battery capacity" and "You can't have too much solar" are just plain wrong and misleading. 😞

RJ was quite right about not getting too much battery for what you can recharge in the time allowed. You can also have too much money invested in solar if you get to Float before lunch all the time.

The proper answer is always, "It depends" (on the scenario).

We have a good body of data here to say how many AH you can replace in how much time using various charging rates (amps vs AH capacity), charging profiles, with the available generator VA power, on Wets or AGMs.

Give us the situation, easy to give the answer for a particular allowed gen time. (You have to start with that--everything can't be a variable. Allowed gen time is one thing you can't control, so must adjust your set-up for. Other things you can't control are RV limitations on number or weight or size of batteries and generator weight and size--but it could be said you can always choose a different RV for the requirements that can carry or fit those.)

Most start out with the chosen RV and then learn afterwards what they can do. No problem, just plug in the facts of the situation, and what you can do in the time allowed can be calculated. If you don't like the answer, get a different RV or go where there is more gen time allowed.

[BFL13]

deleted

[jake2250]

Sounds like a plan!! By all means HAVE FUN!! What race are you going to? I have camped at Sonoma,Fontana,and Vegas, Only needed the heater in Vegas! Got cold in the desert! Have been to Phoenix,Charlotte and Martinsville also,, I sure wish I could camp at Martinsville that place looked crazy at night! Some day we might rent a motor home and go to Talladega!

[pnichols]

elmerfudd51 wrote:
thanks guys for your input. plugged it all in to a spreadsheet (to get a logical result).

1 vote four 6 volts(sounds good)
1 vote two group 31(thats gonna cost)
1 vote three group 31 and party till midnite(im in bed by 9)
2 votes one group 27(two guys agreeing, now were getting somewhere)
3 votes two 6 volt(that was one of my choices)
5 votes two 12 volt(my other choice)

so two 12 volt batteries it is. and if this doesnt keep me warm all nite, i have alternative improvements in mind thanks to you guys.

put more stickers on my genny
get a small solar charger/dumptruck assembly
get a larger solar array/without dumptruck

seriously, thanks to all

Hmmm ..... arent' "two 12 volt" and "two Group 31" the same thing???

If at all possible to fit them, I never use any 12 volt batteries except Group 31. If you can possibly fit Group 31(s) into the battery area ... go for the big guy(s).

Remember the Old Chinese Proverb I made up some time ago: "You can't have two much battery capacity on board .... just maybe more than you can afford or fit". Our current RV uses (only) a couple of Group 31 12 volt deep cycle batteries because that's all that will fit without me stealing storage space needed for other things.

By the way, not all Group 31 batteries are the same .... they range in amp hour capacities from around 100 amp hours each all the way up to around 125 amp hours each. For an RV using lead acid technology batteries - always use deep cycle batteries and always use batteries that are the heaviest in weight for the given size that you want to install.

[pianotuna]

Hi elmer,

You forgot the vote for an 8D.

Since you decided on 2 12 volt, now you need to decide on flooded or AGM. Be sure they are wired in a balanced manner.

Personally I think there is no such thing as too much capacity. I'm at 556 amp-hours of AGM telecom (used but in GREAT shape).