Single big battery v/s 2 batteries in parallel

Too late now, but it is better to not take the single 12v battery the Dealer issues with your new Rv, but instead get a money credit for that, which you can use to help pay for the batteries you really want/need. (like two 6s or whatever you prefer)

As it is, you can indeed get a second one while the first is still fairly new and it will be fine to run them together.

Having more AH is great, but it also means you need to recharge more AH back in. Which is worth another dozen threads! :)

A 8-D is a huge battery weighing 160 lbs and having around 250 ah. I have one, love the capacity but moving it is heck.

Grp 24 is generally the smallest deep cycle we use, having on average 75 ah or so.

Grp 27 is a bit larger and mine is 95 ah.

Grp 29 and 31 are larger still but not that much more in amp hours and not as much as two grp 24.

6 volt batteries have to be run in pairs, have the same footprint as the grp 24 but taller. They are 200+ ah but take two for 12v.

So two 6 volt will do better than most 12v pairs in amp hours and last longer too.

Being new to this, I need assistance with the jargon to understand what is being said.
What does 8D vs 2 x 27 mean?
What does 6s 12s 24s mean? Are we talking voltages?
My trailer is a 12v system so I would be looking at 2 12v in parallel.
I am not looking for power, I am looking to extend amp-hours (which I figured is AH).
Can a physically bigger single battery give me close to as much AH as 2 physically smaller batteries in parallel?

From what I read, it is a bad idea to have an old and new battery in parallel, so since my battery is relatively new, it would be better to buy the second battery now rather than have to buy 2 sooner than later.

Is this an 8D vs 2x 27? Or what size are you talking about?
Do you need max battery?

Matt_Colie wrote:
Steve,

If you put two lead/acid batteries in parallel, you will not get battery X 2 for power. You will be lucky if you get X 1.5. I could explain this, but I have so many times and I just don't feel like it right now.

Matt

I am sure we would all like to know that explanation if you find the time, since everybody else gets more than twice the AH capacity by twinning their batteries in parallel.

Besides getting 2x the AH, you will be running any load at a lower percentage of the capacity than before with just the one battery, so Mr Peukert gives you a bonus, and you get more than twice by doubling.

SKSCCI wrote:
Get 2 batteries and put them in parallel, or the one big battery and not bother with fussing with dual battery issues?

I doubt it matters that much.

The bigger question is: do you dry camp? If not, get the cheapest 12v battery you can find.

If you mean 24s by "small" then note that you can fit two 6s where the 24s will go as long as you have room above for the somewhat taller 6s.

Two 6s in series gets you 232AH (they vary between 208-232 roughly) while your two 24s (85AH each?) in parallel get maybe 170AH.

There are a million threads on 12s vs 6s but there is no dispute about the AHs you can get either way. Of course you can get a pair of bigger 12s to match the AH of a pair of 6s--but in your case you can't fit them on the tongue. Although others have made bigger trays on their tongues to hold more of a battery bank.

Steve,

If you put two lead/acid batteries in parallel, you will not get battery X 2 for power. You will be lucky if you get X 1.5. I could explain this, but I have so many times and I just don't feel like it right now.

Matt