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FrayAdjacent View Drop Down
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Posts: 31 		Direct Link To This Post Topic: Battery sugesstions
    Posted: 18 Jun 2018 at 9:42pm
Normal safe depth of discharge of AGM cells is 20% (80% discharged), not 50%. Lots of antiquated knowledge out there....

Per http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

"The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life. The negatives are slightly lower specific energy and higher manufacturing costs than the flooded, but cheaper than the gel battery."

Again, I still assert that for an RV with very low power demand, an AGM 12V battery is perfectly fine. You can find them up to 230Ah, but they get pretty heavy. 

As for Lithium cells, I watched a video where a couple in their RV replaced their AGM batteries with 200Ah of lithium cells (2x100Ah cells). Cost about $2000, but the cycle life (3000-5000 cycles) compared to the AGM batteries they were using... it worked out in favor of the lithium batteries over a 10 year period..  The number they showed was about $6000 for AGM batteries over the same period.

They did also run a large inverter off of their batteries, and could (and sometimes do) run their AC off of the battery bank. 

My 100Ah AGM battery cost about $160.. I'd have to go through 6 of them in a 10 year period to compare to the lithium. Also a lot of lithium cells like to be charged at a higher voltage than lead acid cells. I think I'll get more than a couple years out of my AGM battery just fine. I'll use my generator to power heavier loads. 
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Posts: 6128 		Direct Link To This Post Posted: 18 Jun 2018 at 7:14am
Originally posted by FrayAdjacent

The logic behind using 2x6V batteries is antiquated. That's a great solution for drawing huge amounts of current, like in a golf cart. And compared to flooded cells, they were more robust. 

AGM batteries are going to be as good if not better. I use a single 100Ah AGM battery. I also use a 100W solar panel with a cheap PWM charge controller. My few trips so far I have not had connections, so I used a generator, but mostly left the converter breaker off. The solar panel should maintain the battery well enough. 


actually.. no. The logic for 2 GC2's continues to be the power density and cost. While AGMs are very robust, they don't solve the density issue, and cost significantly more then a standard flooded cell.

When you start dealing with people who don't use a generator, are actually boondocking with solar, 12v batteries are very rarely used. Your 100aH AGM battery is still a lead acid battery, and not a true deep cycle, so you have around 50aH's available before damaging the battery. a pair of GC2's will cost less (often under $80 a piece) and have over 100aH's actually available with no damage to them.

Specific to the R-Pod, there isn't room on the battery tray for more then 2 12v of the Group 24 size. So, while you could get more aH's if you go with larger 12v's, say group 31's, you can't put two of them on the Pod easily. Or heck, roll big and figure out how to mount a couple 8D's.. LOL

The FUTURE is going to be LifePO4.. but as of yet, the price is still to high. The energy density, and the rate at which they can be discharged, allows them to be used as a back up to actual mains power. Some RVers have made the switch, and are reporting excellent results, even being able to run the a/c, in the desert, without a genny or shore power, but, they have +$8K tied up in the system.
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FrayAdjacent View Drop Down
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Posts: 31 		Direct Link To This Post Posted: 18 Jun 2018 at 12:42am
The logic behind using 2x6V batteries is antiquated. That's a great solution for drawing huge amounts of current, like in a golf cart. And compared to flooded cells, they were more robust. 

AGM batteries are going to be as good if not better. I use a single 100Ah AGM battery. I also use a 100W solar panel with a cheap PWM charge controller. My few trips so far I have not had connections, so I used a generator, but mostly left the converter breaker off. The solar panel should maintain the battery well enough. 
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Posts: 9 		Direct Link To This Post Posted: 17 Jun 2018 at 7:05pm
Originally posted by furpod

If you don't intend to boondock, any single 12v battery will do, it's duties will be to buffer high draw, ie: the slide, and to lock the brakes in case of a runaway trailer. That's it. If you DO intend to boondock, you want as many amp hours of storage as you can get. On an R-Pod, without doing any structural mods, that means dual 6v GC2's. If you solar panel has a built in controller, you can attach it to the battery with alligator clips, or find/buy/add a connector that matches the Zamp inlet (it's called SAE, and a connector can be found almost anywhere)


I decided to go with a single 12v battery. I think the renogy solar panel with an mc4 to sae adapter would be a nice option for boon docking as well. We do intend to boon dock quite a bit so solar would be a nice clean option. I also have access to some Honda generators if nessacary as well although that would be my last option solely due to the noise.
Thank you to everyone for their input!
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Posts: 6128 		Direct Link To This Post Posted: 17 Jun 2018 at 3:13pm
If you don't intend to boondock, any single 12v battery will do, it's duties will be to buffer high draw, ie: the slide, and to lock the brakes in case of a runaway trailer. That's it.

If you DO intend to boondock, you want as many amp hours of storage as you can get. On an R-Pod, without doing any structural mods, that means dual 6v GC2's. If you solar panel has a built in controller, you can attach it to the battery with alligator clips, or find/buy/add a connector that matches the Zamp inlet (it's called SAE, and a connector can be found almost anywhere)
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Posts: 9 		Direct Link To This Post Posted: 17 Jun 2018 at 11:24am
We have the Lensun folding Solar panel

Do you plug this in straight to your battery or do you use the zamp system on the rpod
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Posts: 1447 		Direct Link To This Post Posted: 17 Jun 2018 at 10:23am
We boondock a lot.  Our favorite campgrounds are in National Parks and have no hookups.  (Not like boondocking in the middle of nowhere, but still, no electricity, water, or sewer.  The campground roads are paved and there are restrooms with flush toilets though.  No showers.)  We have 1 12v battery, but we also have a generator, and depending on where we're going, I take a Renogy 100w suitcase.  There is no limit as to how long we can stay out as far as battery power is concerned.  Two 6v GC batteries might smooth out the cycles some, but they aren't needed in our situation.

A generator is a lot to lug around and you can't use them during quiet hours, or at all in some campgrounds, plus, even with a quiet Honda or Yamaha, they annoy people.  They conflict with the concept of getting away to a quiet campground in the mountains, desert, beach, etc., even for the people who have them, at least to some extent.  So they aren't for everyone.  Some people have to have air conditioning though....  (We very rarely use the air conditioner, so we might run the generator for an hour or two a day, to make coffee and top up the battery.  Even that is moderated depending on how many and how close our neighbors are.)

No matter how many or what kind of batteries you have they will eventually need recharging.  Solar can be a very viable solution if you don't need more than a few watts of 120v AC, which you can get from a 400w inverter.  (To watch television, for example.) 

Towing all day seems to top off my battery pretty well, but that doesn't work when you're at your destination for 8 days.  Without very careful and stingy power management, 2 6v GC batteries won't last that long. 

I started out wanting to say that 1 12v battery will work just fine as long as you have some way to charge it up every day or two or three.

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Posts: 128 		Direct Link To This Post Posted: 17 Jun 2018 at 9:12am
Here is my take.

R-pod will come with 1 12 v deep cycle.
I have a second 12 v Deep cycle for my trolling motor.

Why should I stash those and spend money to buy 2 6 volt batterys?
Will they hold more than my 2, yeah, maybe. Enough extra to be worth spending 250$ on?

Not in my current opinion.

Currently I have lots of options.  I can run a single 12v recharge with solar and when the battery gets low, spend a night in a campground. Empty tanks, fill water, watch some TV. Run the AC.

I can leave a single 12 V hooked up and carry a full spare. So if we run out of power, we have extra on tap.

Or I can wire it in.  Ideal, perhaps not, but remember, repurposed battery, no additional cost = does not have to be super efficient. Just has to carry its weight.

We have the Lensun folding Solar panel.

Not cheap, but if it doubles our boondock time from 2 days to 4. Worth every penny.

So that is what I'm planning. Down the road if and when I would have to replace a 12v battery would be the point to switch to dual 6 v golf cart batterys IMO.

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Posts: 3257 		Direct Link To This Post Posted: 16 Jun 2018 at 8:34pm
Although I may consider a pair of 6v golf cart batteries in the future, the current (2) deep cycle group 24  12volt batteries are still going strong as they are now over 7 years old.  We still get 3 - 4 days out of each before switching to the other and this is when night temps are in the 40's or less and the furnace is running a fair amount.  
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Posts: 83 		Direct Link To This Post Posted: 16 Jun 2018 at 5:31pm
Upgrade to a pair of quality 6-volt golf cart batteries and a PD converter upgrade and never look back. 
Michael
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