Battery series/parallel questions...need advice/info

[spezzez]

I mainly boondock camp vs hooking up in an rv park. I have a brand new fully charged Super Start Marine Deep Cycle 12-volt, 27-group battery; and a brand new fully charged Exide 12-volt, 24-group Deep Cycle rv battery for my 2010 28 foot Gulf Stream Innsbruck-Lite travel trailer. I want to connect the two batteries in series or parallel. Since the trailer is a 12-volt DC system, I assume I want to increase my amp hours and not my voltage, right? Does it matter that one is a 27-group and one is a 24-group, since they're both 12-volt batteries? Finally, do I want to connect them in series or parallel? Thanks in advance for any info.

Spezzez

[Passin_Thru]

This is easy. Think of it as water. Water flows to the least resistance. Water will stop flowing when you close the valve, unless there is a leak. Water goes the way you push it same as when you generate. You should check your water and add some when it is low, even in 3 months and not blame your charger like RoyB. You can always go to a Class 8 truck battery to replace both 12 v batteries.

[time2roll]

Parallel. Next will be 100+ watts of solar.

The 12 Volt Side of Life

[CavemanCharlie]

spezzez wrote:
I suppose my main concern was the fact that they are different battery groups. Just needed more info on that since it's hard to find info on that using google search. So I figured I might as well just ask all questions to experienced more experienced rv owners than I. We just bought this TT two weeks ago, and before that had a vintage 1958 Aljo that we restored and fixed up. It didn't have a battery and just plugged into a generator for lights...no furnace, no bathroom...truly boondocking. Our family has and is growing so had to upgrade, so been learning as much as I can, and fast. That said, experience is the best teacher, but would prefer to learn beforehand from others'experiences vs on my own the hard, expensive way where possible. I'm thankful for you all and forums like this one! And youtube, lol.

And thank you for learning how things work first.

To many people go out unprepared, have trouble, and then complain. I respect the fact that you are trying to learn how things work before hand.

[spezzez]

I suppose my main concern was the fact that they are different battery groups. Just needed more info on that since it's hard to find info on that using google search. So I figured I might as well just ask all questions to experienced more experienced rv owners than I. We just bought this TT two weeks ago, and before that had a vintage 1958 Aljo that we restored and fixed up. It didn't have a battery and just plugged into a generator for lights...no furnace, no bathroom...truly boondocking. Our family has and is growing so had to upgrade, so been learning as much as I can, and fast. That said, experience is the best teacher, but would prefer to learn beforehand from others'experiences vs on my own the hard, expensive way where possible. I'm thankful for you all and forums like this one! And youtube, lol.

[spezzez]

Thanks everyone for the info. I had already done alot of searching, reading, watching videos, and asking my techs at my local rv dealer, but thought I'd ask on here for more perspectives and info before I do it. I appreciate your time to help me out!

[pianotuna]

Welcome to the forums.

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.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?

Here is a video of 3 twelve volt batteries that have been wired in an unbalanced manner for 2 years. They have been equalized. The test shows how CCA has been adversely affected.

unbalanced for 2 years

[RoyB]

The GC2 6VDC GOLF CART GP24 Battery when connected in series gives you a good 225AHs of battery capacity for a good cost. This is essentially a 12VDC BATTERY after two are connected in series. The GC2 GOLF CART BATTERIES have larger cores inside and will produce a good long source of 12VDC for the cost involved.

Your trailer requires 12VDC so this means if you buy the 6VDC GOLF CART batteries you have to connect two of them in series to come up with the required 12VDC battery source.

To gain more AH capacity using the 12VDC battery then you must connect additional 12VDC batteries and connect them all in Parallel to maintain the required 12VDC the trailer wants to see...

When I got my OFF-ROAD POPUP Trailer setup in 2008 I started out with 4EA GP24 12VDC Interstate 85AH batteries mounted in parallel giving me a total 340AHs of battery capacity. This only lasted about three months as my single voltage on-board converter/charger unit boiled out the battery fluids of one of the batteries which shorted out the cores which I did not catch quick enough so I just pulled it from the setup. I changed out my old converter/charger unit to a PD9260C smart mode unit and have been running my 255AH battery capacity setup now since 2009. My GP24 Interstate batteries are just now starting to fall off on performance i.e. not holding the charge like they used to.

LOTS OF INFO on-here about this subject - do some searching and reading...



Roy Ken

[gbopp]

Welcome to the forum.

Here's some additional info on batteries and 12 volt systems:
The 12 Volt Side of Life.

[westend]

You only want to connect them in parallel. Connecting them in series will damage circuit boards and other devices in your trailer. Two dissimilar batteries will not charge/discharge 100% correctly but we all must do what budget allows.

Good info here at Battery University

[Grandpere]

It would be better to have both of them the same group, but you an get by with connecting them in parallel. Parallel give you 12 volts and extra amp hour capacity of both batteries added together; in series you would have 24 volts (12 plus 12) and only the max amp hour capacity of the smaller battery.