Two Batteries in Parallel Questions

[chewman]

Folks,

I have a WD2650BH and I'm going to be dry camping for 10 days. I want to put in a two battery - parallel system, but my head is spinning from reading articles about batteries.

I would like to stay with 12v. I don't want to spend a ton of money and I'm not quite sure what to get.
I currently have an Exide 24MDPST that I would be replacing with this 2 battery solution. (I'd like to stay around the same size to ensure I have room on the tongue for two batteries.)

Do I go with Deep Cycle? Do I go AGM? What brand/model do you fine people recommend?

Thanks in advance and happy camping!

 

[avvidclif]

AGM if your pocketbook supports it. Most new chargers support AGM charging and they are designed for exactly what you will be using them for.

 

[Jim.Allison]

Go buy yourself some industrial deep cycle Trojan batts. You won't be sorry, If you have space limitation where your compartment can't be ventilated then get AGM, if you have a ventilated space get flooded lead acid. IMHO FLA's are always better than AGM.

The main question is how will you be charging them? And what kind of cabinet space do you have on your rig?

You are not buying anything but amp hours. It is amp hours per dollar. Not batteries per dollar.

 

[chewman]

I have a Honda generator (EU2000i) I'll be using for certain hours out of the day, while camping. I'd like to have no maintenance and they'll be mounted on the tongue in the plastic black boxes. (There's just enough room I think, to have 2 batteries side by side...but they will need to be the size of the Exide 24MDPST that I will be replacing.)

 

[JohnD]

We had dual batteries mounted side by side on the tongue of our previous 2013 Heartland Trail Runner . . . there was plenty of room!

You can see them at left in this photo:

 

[chewman]

I just had a phone conversation with a couple people at Interstate Batteries and they suggested 2 x 6v batteries in series. It'll give me a ton of run time. They were the GC2-XHD series. Has anyone ever run golf car batteries for their campers?

 

[justafordguy]

Yes, lots of people do and they will give you more capacity for your money and last a long time.

 

[Jesstruckn/Jesstalkn]

I just had a phone conversation with a couple people at Interstate Batteries and they suggested 2 x 6v batteries in series. It'll give me a ton of run time. They were the GC2-XHD series. Has anyone ever run golf car batteries for their campers?

Yes 2 6V Batteries will give you a lot more run time and last a lot longer. IF you properly maintain them, meaning adding distilled water once a month on normal use, and twice a month on heavy use. That's not for me. If you do go with 6V Costco has them for about $90 each.
I chose to go with 4 12V and 320W solar. I'll See how long they will last.

 

[scottyb]

If you are going the cheap route, go with 2 GC-2's instead of two 12V marine batteries. If you are going the medium price route (true deep cycle lead acid, I.E. Trojan) 6V vs 12V is a toss up. Same thing can be said for High-end AGM's.

 

[Lynn1130]

Most of us who boondock run at least 2 6 volt batteries and some who have the room have 4 or more. 2 work fine for us and we camp up to 2 weeks in the boonies. The generator usually runs for a bit each day and sometimes longer if we decide to watch a movie so they stay charged during the camping trips.

 

[Bohemian]

AGM has lower capacity then standard deep cycle batteries for the same weight or price.

AGMs have far less maintenance. Can usually be mounted inside closed spaces and in any position including on their sides and upside down (check battery specs)

100 lbs of 12V or 6V batteries should have about the same capacity. 2-6Vs are easier to handle. 1-12V has fewer cables and connections, but is twice the weight per battery for the same total capacity.

 

[Jim.Allison]

while it is traditional to run 2 GC batts, depending on your space you can actually get more out of 2 12v batts. About the best 6v GC batts in series will yield 225 amp hours (112 usable), you can get 2 12v, and run parallel and get 300 amp hours (150 usable).

It is purely a function of amp hours vs dollars. Battery technology is almost perfected and there are only X amount of amp hours that can be produced from X LBS of lead no matter the configuration.

Cells do go bad, if you lose a cell in one of two 6v, you will have to get an identical 6v to replace it, if you lose a cell in a 12v, you can continue to function on a single batt.

The combination 12v RV/Marine batts are worthless in that you can only get about 210 amp hours out of 2 in parallel and only 105 is usable. Once you buy you have committed yourself, I would strongly suggest that you see if you can work a deal on a pair of trojans, or continentals or some other industrial deep cycle battery, 6v or 12v depending on your preference.

 

[Jim.Allison]

Generators are very efficient at running your charger through the bulk charge stage of your charger/converter stages. Anything after bulk charging is a waste of fuel. Your generator can run all day and not top off a battery set. So run your batts down to 50% discharged, and use the efficiency of the bulk charge to bring them back up (of course if you have occasion to run your generator for some other purpose, so much the better). You don't have to top them off on every cycle, just top them off before storing them, and keep them topped off during storage. Don't run the batt frequently below 50%. You can go less if you have to, but keep in mind that you are giving up battery life if you do. Battery life diminishes EXPONENTIALLY based on how deep the average cycles are. The accumulative effect is what you are trying to prevent. Batts can cycle 1000s of time if they are discharged only 10%, discharging 50% on every cycle brings you below a 1000 cycles, and discharges to 20% brings your life in cycles in the low 100s. So 50% is your mark for life and $$$. Its the average you need to worry about, one incident to 20% is not going to shorten the life of your batt in terms of years on your rig.

I have a Honda generator (EU2000i) I'll be using for certain hours out of the day, while camping. I'd like to have no maintenance and they'll be mounted on the tongue in the plastic black boxes. (There's just enough room I think, to have 2 batteries side by side...but they will need to be the size of the Exide 24MDPST that I will be replacing.)

 

[Lynn1130]

And when you go to load and unload these batteries keep in mind that 12 volts are at least 20lbs per battery heavier as I recall when I was researching.

A search will bring up volumes of threads on this topic.

 

[pegmikef]

I have a Honda generator (EU2000i) I'll be using for certain hours out of the day, while camping. I'd like to have no maintenance and they'll be mounted on the tongue in the plastic black boxes. (There's just enough room I think, to have 2 batteries side by side...but they will need to be the size of the Exide 24MDPST that I will be replacing.)

When we boon docked in our TT I took two six volt Trojans out of my golf cart and used them (about 40 plus pounds each) and would run my Honda 2000 about three hours a day (in conjunction with wife's hair equipment) and it would bring my batteries back up to 13 plus volts, but I just hooked up the shore power line to the generator so it was the converter charging the batteries.

On edit, I did have to buy different battery boxes to to accommodate the six volt batteries. I got them from J.C. Whitney.

 

[avvidclif]

It is purely a function of amp hours vs dollars. Battery technology is almost perfected and there are only X amount of amp hours that can be produced from X LBS of lead no matter the configuration.

.

Au contraire. Have you looked at the new Li-ion batteries? It's a whole new ballgame.

Here's a link: http://www.lithiumion-batteries.com/products/12v-100ah-lithium-ion-battery/

That's for a 100AH that weighs 28 lbs. The 300AH weighs 93 lbs. What would the equivalent lead-acid weigh?

The DOD (depth of discharge) is much better and doesn't hurt the battery (90%). And on and on....

 

[Lynn1130]

Sorry but I have heard and seen too many horror stories with li-ion batteries and RC aircraft. They are basically unstable at times and the airlines refuse to transport them because of that. Do you want one charging under your bedroom? Not me. Do a search on RC aircraft and Li-ion fires. We charge those things in fire proof bags because of the danger and never leave them alone while charging. I use them if RC aircraft but there is a process that you must follow to be sure you do not end up with a fire.

 

[Jesstruckn/Jesstalkn]

Au contraire. Have you looked at the new Li-ion batteries? It's a whole new ballgame.

Here's a link: http://www.lithiumion-batteries.com/products/12v-100ah-lithium-ion-battery/

That's for a 100AH that weighs 28 lbs. The 300AH weighs 93 lbs. What would the equivalent lead-acid weigh?

The DOD (depth of discharge) is much better and doesn't hurt the battery (90%). And on and on....

I viewed the link, and they look like the new in thing (I want that) ... but at $1200 up to $2000 a battery I'll wait tell they come down in price and have proven themselves in this application

 

[avvidclif]

Sorry but I have heard and seen too many horror stories with li-ion batteries and RC aircraft. They are basically unstable at times and the airlines refuse to transport them because of that. Do you want one charging under your bedroom? Not me. Do a search on RC aircraft and Li-ion fires. We charge those things in fire proof bags because of the danger and never leave them alone while charging. I use them if RC aircraft but there is a process that you must follow to be sure you do not end up with a fire.

Not the same battery, these are polymer lithium ion. They have built-in charge controllers for each cell. The Rc battery problems are due to way too fast charging, trying to cram a 12-16 hr charge into 1 hr. It does cause problems. Especially since the cells are tied together with no method of controlling the charge to each. Read more about the technology.

Yes they are pricey, now. I was just pointing out that the state of the art for batteries is nowhere near finished. Lead acid is dead, thanks to the EPA.

 

[Jim.Allison]

"Au-Contraire"? LOL. That is an awkward statement, since I was not comparing Pb to Li. Lithium ion would be the best, but like I said "there are only x amount of amp hours that can be produced from X amount of lead, no matter the configuration." All I have to say about Li-ion is do the math and if it works out then it is a good purchase. BTW 300 amp hours in FLA is about 166 lbs for good good quality FLA batts.

It is important to list all the components that will be required to install a FLA system vs a Li system. You can buy one Li batt, and no interconnecting cables. But you need a programmable charger. But again, the lifespan of a Li batt is incredible. And there is no maintenance. So you do bring up an interesting topic. Li-ion is going to get a lot cheaper and soon with Elon Musk's "Gigafactory". I suspect that this will soon replace Pb acid batts as the go-to batts for RV-DC systems.

Au contraire. Have you looked at the new Li-ion batteries? It's a whole new ballgame.

Here's a link: http://www.lithiumion-batteries.com/products/12v-100ah-lithium-ion-battery/

That's for a 100AH that weighs 28 lbs. The 300AH weighs 93 lbs. What would the equivalent lead-acid weigh?

The DOD (depth of discharge) is much better and doesn't hurt the battery (90%). And on and on....