I know this topic has been beat to death and have read as many of the archived threads as I could. But my question is this: I am replacing my trailer batteries. Costco has group 27 12v batteries rated at 115 AH. 2 of those would give me 230 AH. 2 6v batteries will give me 220 AH. Price is about the same for the 2 types.

Question 1. Are the 6v still the better choice? Will they hold a charge longer than the batteries listed above?

Question 2. Do 12v batteries have to be installed in pairs? Has anyone ever run 3? That would give me 345 AH of power.

Thoughts?

My personal experience has been stellar with 6v. I have had multiple trailers with multiple 12v setups and they have always gone dead for one reason or another. I switched over to 6V 3 years ago and they have NEVER gone dead, not once and I do stupid stuff like leave my stereo on all day, lights on, run heater all night.

I agree with the 2, 6 volt batteries idea. When I had my trailer, my wife would run the heater like crazy and with the 6 volts, we never had a problem with dead batteries. I also think Costco is the way to go because of their liberal return policy.

Well, you get more amp hours out of the 12v setup, but the 6v setup will probably handle more cycles. I'd go with the 6v setup, as 10Ah isn't that much in the grand scheme of things.

Go with two 6V. You will be glad you did.

Here is a link on how to connect batteries.

http://www.usbattery.com/usb_config.html

If I were to replace my 12V with 6V on my trailer, are there any changes I have to make to the trailer, as far as the wiring goes? If I hook up two 6V, do I still connect positive to positive, and negative to negative?

I have costcos in my trailer and they work great.

How you wire them

Your best off with (2) 6 volt batteries. Going with (2) 12 volt is twice the number of battery cells and if one goes bad it draws down the remaining cells. Wire the two batteries in series see above link config #1.

6 volts, and yes you can hook up 3 12v's. 6volts have to be in pairs 12volt don't

So would two six volts be enough, or would I need four? (20 ft carson toy hauler)

Glamis girl, Im using only 2 6V's in my 40footer. I think that will more then plenty for your trailer. If you get an inverter, you may never need to turn on the generator! I could use 2 more batteries on mine though.

I'm just waiting for my 12v's in my trailer to need replacing and I'm definitely switching to 6v's. I put 4 of them in my boat for the stereo and couldnt be happier:

Thanks!

Rockwood, that is a wrong statement. Almost all 6V deep cycle batteries have more Ah or cranking amps than do 12V batteries.
Now, to answer the OP's question, just as in a car, you can have a single 12V battery, not highly recommended, but doable. I worked at Beaudry RV for awhile after I retired from the Air Force, because I was tired of aircraft work.
A lot of the trailers, both tow behinds and 5er's, had 4-6V deep cycle batteries. At least the ones that had a large 12V load capability, anyway. Some of the bigger ones even had a large inverter to run the microwave off of the batteries. If you go dune camping alot, I would highly recommend 4-6V batteries, and a solar panel for the roof. If you leave the trailer parked, the solar panel will keep the batts. charged fully. The panel will also charge the batts. while you're out in the dunes playing. I have this set-up, and I only run my generator about 1-2 hours a day. And during my entire week at the dunes, I never have a battery issue. This is taking into consideration that it's cold as a well digger's a$$ when we've been out there trying to keep a 39' long, 13'5" tall toyhauler warm enough for my wife. (she's cold at anything under 75*).

Just my educated $.02

BBTank

Err, I got that info (more Ah) from the OP's first post:



So unless he posted incorrect information, it's not a wrong statement.

Either way, yes, most 6v batteries have more Ah than their 12V counterparts, but since they're 6v, you don't add their ratings when hooking them up in series to make 12v. 2 220Ah 6V batteries would be 220Ah @ 12V and 2 110Ah 12V batteries would be 220Ah @ 12V. The easiest way to compare these would be to compare VAh instead of just Ah.

I just bought 4 6v from Sams club for my MH. 71 bucks a piece.

IIRC 6v batteries have thicker plates, which means they can take more charge/discharge cycles than a comparable 12v. You have to stay on top of the maintenance though.

The 2 6v Trojans in my moho are over 5 years old now, they're showing their age but they still hold a charge for a weekend. In my toyhauler, I had to replace the 12v batts at 3 years, dead as doornails.

Yep. By design, they'll have thicker plates since it's the same size battery with half the cells, which IIRC helps them last longer per charge. They've also got more room under the plates to make them last longer overall, since as the lead falls off, it takes longer for it to short a cell out.