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furpod View Drop Down
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Post Options Post Options   Quote furpod Quote  Post ReplyReply Direct Link To This Post Topic: List Your Mods:
    Posted: 07 Aug 2015 at 12:44pm
Pretty happy with the new battery layout..



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techntrek View Drop Down
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 07 Aug 2015 at 11:29am
The imbalance doesn't happen with 12 volt batteries in parallel if you follow the steps I listed above.  I'm active in a solar forum where members do it all the time (paralleling strings of batteries, where any imbalance would be magnified).  The problem comes in when you use dis-similar wire (gauge and/or length), batteries that aren't identical, or wire up the charge/load to just one of the batteries.

That said, if you were starting out fresh, two 6 volt batteries in series is easier.  Not more amps necessarily as some think - pound for pound you get the same amps from the lead surface available.  But the 6 volt golf cart batteries tend to be heavier, because they are all deep cycle where total amps is the goal (and not motor starting, although you can do that with deep cycle if you oversize them 20%).  

Plus the Peukert Effect kicks in with paralleled and series batteries which gives you more total amps than the sticker rating of the two by themselves.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Post Options Post Options   Quote JandL Quote  Post ReplyReply Direct Link To This Post Posted: 07 Aug 2015 at 10:22am
12 volt batteries wired in parallel.
This is to answer Fwunder question about two 12 batteries wired in parallel. When you start with new batteries from the same manufacture and the same group size and you wire them in parallel they will be in voltage balance, but as the batteries age and the cells get weaker, and the specific gravity of the electrolyte changes the two batteries won’t have the same internal resistances, so the higher voltage battery will discharge through the weaker one. Once the stronger battery voltage drops to what the weaker battery is they will be in balance and the discharge will stop. If one of the batteries failed early and has to be replaced you have the problem of, do you replace both at the same time or have a brand new battery and an older battery?

Single 12 volt batteries and two 6 volt batteries wired in series do not have this voltage balance drain problem. Two 6 volt batteries wired in series has 6 cells at 2.1 volts each (12.6 volts) just like a single 12 volt battery. For me the single battery also means less tongue weight. A group 27 battery is about 51 pounds and 90 amp hours, a group 31 battery is 60 pounds and 100 amp hours. A group GC2 6 volt battery is 67 pounds (x2=134 pounds) and 200+ amp hours, that is the same amp hour rating and weight as a single group 4D battery. If I was to go to a 2 battery setup I would use two 6 volts wired in series. At 67 pounds each I think my wife and I could lift them in place. We could not lift a 4D battery.

So for me the advantage of a single battery is it is simpler to maintain and check one battery, less weight on the tongue, you don’t have the batteries trying to match the voltage of the weaker one as they age and if the battery has to be replaced you don’t have the issue of do you replace both of them.

Another thing to remember about normal wet cell batteries and it doesn’t matter if you have one or many, is they all have a self-discharge rate, about 2-4% per month, so this is why you must maintain your batteries and kept them charged, because if you just let them sit they will die on their own.
JandL
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 8:40pm
Sorry it wasn't clear.  To put it another way, if you attach the positive and negative to the same battery (after paralleling them), then you will encounter the charge and discharge imbalance the poster on the prior page was talking about.  So you must attach to the positive of one battery and the negative of the other.  Also you need to be sure the paralleling wires and the positive and negative wires are the same length.

But this is all a non-issue with 6 volt batteries in series.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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Post Options Post Options   Quote sailor323 Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 4:57pm
Originally posted by techntrek

Fred is correct.  Adnd if they are two 12 volt batteries they must be wired correctly (+ to one battery, - to the other battery).  Then they will be fine.


techntrek, I know you know what you are talking about, your infois always spot on.  This post is a bit unclear.  Just to clarify matters, if you have two 12 volt batteries and want a 12 volt bank of batteries, connect the positive of each battery to the positive of the other and the negative of each battery to the negative of each battery.  Take your power from the positive and negative of either battery.  Actually, I like to take the power from the positive of one battery and the negative of the other.  I attach the charging cable the same way, positive of one battery and the negative of the other. 

If you have two 6 volt batteries and want a 12 volt bank, connect the positive of one battery to the negative of the other, then take your power from the remaining posts.

I know that you know this but I felt your post didn't state that clearly.  I just didn't want someone to become confused.


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Post Options Post Options   Quote furpod Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 4:51pm
Originally posted by ilthyn

Not sure what you mean by powering an inverter off my Ram. It does have a 110v outlet in the cab but it is limited wattage. The solar is free and silent.



I think he means why not hook an inverter to the Ram's battery, rather than carry another battery to hook it to, which is what you are doing now. It's just different ways to get to the same place.
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Post Options Post Options   Quote ilthyn Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 1:05pm
Not sure what you mean by powering an inverter off my Ram. It does have a 110v outlet in the cab but it is limited wattage. The solar is free and silent.

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Post Options Post Options   Quote furpod Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 12:27pm
Originally posted by JandL

I went with the single battery for simplicity. The problem with multiple batteries is after a while one would get weaker and the stronger battery would discharging into to the weaker battery to try to bring it to the same voltage. I would have purchased a group 31 but Costco doesn’t carry them. Someday when I have to replace it I will go to Sam’s Club because they carry group 31 batteries. Any battery bigger than that, I would need a forklift to lift it in place. I also have a generator, but the solar panel makes no noise.


This simply is not true with matched batteries that are properly wired and maintained. I have more than 40 years working with both small and large multi battery systems, 6v, 12v, and 24v systems, and have never seen this when done correctly.
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Post Options Post Options   Quote Jonknite Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2015 at 10:37am
I too prefer solar charging when possible, I bought an R-Pod because I can take it off the beaten path. There is NOTHING worse than the constant drone of someone's generator when I'm trying to get away from it all.
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Post Options Post Options   Quote techntrek Quote  Post ReplyReply Direct Link To This Post Posted: 05 Aug 2015 at 10:24pm
Fred is correct.  Adnd if they are two 12 volt batteries they must be wired correctly (+ to one battery, - to the other battery).  Then they will be fine.
Doug ~ '10 171 (2009-2015) ~ 2008 Salem ~ Pod instruction manual
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