6V batteries fit in Outback propane tub

ScottG

Right. Sorry, @xbooooo, you did say in your post that yours were both 12V batteries!

And, upon looking back at the beginning of the discussion, I see Tabaz already  answered my question as well as proved the limits of my electrical nerdiness...  :-)

I do believe you could wire two 12V batteries up in parallel (provided they are the same model and age). That would double your amp hours and not require you to switch batteries.

ChrisandAlexis

@ScottG . Your question piqued my curiosity. I was thinking that the amp-hours add together just like you did. When I Googled searched the information, it says if in series then just voltages add up but not amp hours. If in parallel, voltages stay the same and amp-hours add together. Please double check me on this.

ScottG

@ChrisandAlexis, that is my understanding as well.

While I can't 'splain the physics behind it, I'm pretty sure you are correct. Probably has something to do that basic Watts = Volts x Amps relationship.

jkjenn

ScottG said:

Can I safely assume amp-hours (like volts) are directly additive when using two 6V batteries?

In other words do two 75ah batteries provide 150ah total, is is there something more complicated here that I'm missing?

2 12v would work differently, since the voltage must be 12v. You would use one battery, then the other (parallel). You wire two 6v batteries to work at the same time to achieve 12v (series). Each battery has about a 225 ah capacity. You get about half of that, so about 112ish. If you account for about 1/2 usability of 12v batteries, you would get about 75ah of usable battery. The other reason people go with 2 6v is longer life expectancy.

Luckyj

Wow, all this is very nice, but I am surprised that no one has raise the red flag about not tiyng down batteries to the trailer.

specialy at 65 pds.  Those can become canon balls and not fiberglass of or plastic tubs will hold them in place in an accident.  They could even start an electrical fire if they move to much.  And no, unless they are tied down, they can move, no matter how heavy the are.

jkjenn

Luckyj said:

Wow, all this is very nice, but I am surprised that no one has raise the red flag about not tiyng down batteries to the trailer.

specialy at 65 pds.  Those can become canon balls and not fiberglass of or plastic tubs will hold them in place in an accident.  They could even start an electrical fire if they move to much.  And no, unless they are tied down, they can move, no matter how heavy the are.

I think most of us (if not all) do tie them down. 

xbooooo

Good point. I just placed them in there out of curiosity for fit, and to photograph. The battery I actually use is sitting on the ground in lower right of picture. That one is strapped in. 

Luckyj

xbooooo said:

Good point. I just placed them in there out of curiosity for fit, and to photograph. The battery I actually use is sitting on the ground in lower right of picture. That one is strapped in. 

Ok, good.  I will come down now!  Sorry for all the fuss!  

Ratkity

@ScottG, in series, the voltage of 6V is additive to 12V, but the amperage is not additive - 2x 6V at 225 ah is 12V with 225 ah. In parallel, the voltage remains 6V, but the capacity is additive.

Catie

Can someone please post a picture of the two 6 volt batteries connected to the T@B disconnect and the solar?

pthomas745

Here is a thread with some photos....
http://tab-rv.vanillaforums.com/discussion/4313/dual-6v-batteries/p1

And a thread with a Jenn Grover video of her battery setup that might help.

http://tab-rv.vanillaforums.com/discussion/2259/how-to-charge-dual-parallel-12-volt-batteries

Hops

I am just adding my information for the two 6-V CostCo battery install in the front tub of our 2017 320-S.  I was happy to see they just fit. Made floor to fill the space and the well the old battery sat in - for added stability. Pictures are the new plywood platform, and the two battery fit, and the 3rd picture shows that I turned the bolt around on the propane clamp. The 4th picture shows what the bottom of my "tray" looks like so it fit in the old battery tray compartment.

EDITED FOR PICTURE SIZE

ChrisandAlexis

@Hops, interesting that you did not have to remove that white cylindrical pvc thingy in the tub to get your Costco batteries to fit. Our Costco batteries would not fit with the pvc intact. I also had to move the propane regulator.

dsfdogs

I don't see a battery tray? How are they held down? Thanks!

Hops

@dsfdogs the board underneath acts as a tray and I will add photos of the straps that I'll put on. 

Cbusguy

@ScottG It all depends on how they are wired,   2 12 volt 100 amp hour batteries wired in parallel would get you 200 amp hours.     wire them in series you would get 24 volts at 100 amp hours.     

The issue is you can only take lead acid based battery down to 30-50% of capacity before doing long term damage to them.  So the reality of a 200 amp hour lead acid battery bank is 100-120 amp hours which is usable.   just food for thought,    

klenger

^^ That's why I went with a BattleBorn Lithium battery on my 320.  100 AH of usable power and only 30#.  All for the low price of $950

Cbusguy

@klenger While battleborn have a built in battery management system and an impressive warranty,   I am not sure I would take all 100 amp hours out.    For max life most of the battery wall, solar guys are recommending 80%.   Which is still 30 amp hours more and less weight than lead acid.    

I am leaning toward using a tesla module,   24 volts and 250 amp hours.   they weigh 55 pounds.   they are about $1200 for a tested module out of a wreck.    The downside is it is not a drop in install like a battle born,  but what the heck I like to tinker.   So you need to add a BMS and supporting hardware.....

For all that messing around,  how much time do I plan to camp without services?   Not sure yet.     Lots of mathematical fun to make sure it will all work.

klenger

^^ That's why I will also carry a Honda EU2200i generator.   I'm finding that the T@B power requirements are very modest compared to the full size RVs I've had in the past. 

dsfdogs

@klenger I found this volt/% guide in a YouTube comment and confirmed with Battle Born this week-you might find it useful:
13.6V = 100%
13.4V = 99%
13.3V = 90%
13.2V = 70%
13.1V = 40%
13.0V = 30%
12.9V = 20%
12.8V = 17%
12.5V = 14%
12.0V = 9%

klenger

Actually, I installed a Bogart Engineering battery monitoring system to keep track of % of battery charge. I've been using systems like this for about 20 years and, from my perspective, it's the only way to really know your battery condition. 

This page shows some curves for battery % of charge vs voltage for BattleBorn vs lead-acid

https://battlebornbatteries.com/comparison-one-battle-born-lifepo4-battery-two-6v-gc2-batteries-series/

Hops

dsfdogs said:

I don't see a battery tray? How are they held down? Thanks!

My pictures are a bit out of order. The first picture is the bottom of the plywood platform I made. The underside of the platform has another piece attached to it that fits into the small "well" that the original 12v battery sat in. The last picture is the top of the platform. The piece on the bottom that fits into the well adds a lot of stability. 

DaveHaney

I'm about to put 2 6v GC-2 batteries in my 2017 Little Guy CSS-Max tub, and it looks from this thread as if they will fit. Any worries about water getting in without a battery box cover, given the gap between the tub and the T@B? I have not seen a dual battery box that would fit, and there doesn't appear to be room for 2 single battery boxes eiher.

ChrisandAlexis

@DaveH, we have the same year and model T@B. It is a super tight fit with 2 GC-6 volt batteries from Costco. Our tub is a little off after adding the 2 GC batteries. The lid of the tub now scrapes against the front of trailer on the propane tank side when I open the lid to get to the cutoff switch. There is no way I could have the batteries in boxes or a single box and get the whole thing to fit.

Hops

@DaveHaney the two 6-volt fit like a glove in the tub of my 2017 320S. I would not worry about any water. You could create a make-shift cover if desired. 

https://tab-rv.vanillacommunity.com/discussion/comment/110218/#Comment_110218

Hoogie69

I put two Duracell Ultra 6V Deep Cycle Golf Cart Battery (SLIGC125) in my tub.  At 68 lbs each they are a bear to juggle in/out w/o a handle (which BatteriesPlus did not offer).  This gives me a 20 hr capacity of 235AH, more than enough to run my wifes CPAP for 4-5 days if we needed to.  I didn't feel like they would fit w/o downsizing the propane to an 11 pounder.  I did strap my batteries down individually w/ 21 inch rubber bungies (two on each battery) as I didn't want them bouncing around.

DaveHaney

Thanks for all the options! I now have a plan, thanks to you all.