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Old 06-13-2017, 12:44 PM   #1
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Default AGM Battery Questions

I've read most of the posts in this forum, but didn't catch this. My apologies if it was covered elsewhere.

The coach I'm considering comes with two wet cell batteries. At some point I'm going to want to replace with AGM. I was surprised when I went looking that AGM could be had in both 6V and 12V and a multitude of Amps and that they all seem to be physically sized rather randomly.

When I need a battery for my truck, I just drive to NAPA tell them what vehicle I have. The nice person behind the counter looks it up and fetches the right size and I can swap out the batteries on the spot. This is a little different.

What "size" batteries are typical? And by size, I mean volts, amp and dimensions.

Thanks for your help.
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Old 06-13-2017, 01:29 PM   #2
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.

In an RV, there are 2 things you are concerned with:

1. Available space

2. AH


You want to buy the biggest battery(s) you can fit into the available space, because the space is usually limited, and you want as much AH as possible for your RV.

Battery dimensions are sorted into "Groups".
Don't get taken back by the fancy terminology; it is nothing more than a name to describe/standardize different sizes.

First thing you need to do is to measure the space you have.
Or to check the battery in it right now and see if you can find the Group number, and buy a replacement battery of the same group number.


Some batteries come in 12v, and some are in 6v.

If you use 6v batteries,
you will need 2x6v batteries connected in series to produce a 12v service.

If you have more than one 12v battery,
you connect them in parallel to give you more amp/hr service.

There are lots of website that can give you detailed explanation. Let us know if you need more help in this area.
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Old 06-13-2017, 02:48 PM   #3
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Thanks. Just to be sure I understand:

A 12V 200A battery will run my devices longer than a 6V 200A battery, correct? If the amps are the same, is there any benefit to having 6V batteries besides price?

So if I want to replace the existing batteries with two 12V 200A batteries, I think these are the instructions:

1. Check physical dimensions of current batteries. If the current batteries fill the space, I can use the Group Number on them to size the replacements. If the current batteries are smaller than the space allotted for them, I can increase the size of the batteries to fill the space.

2. If the old batteries are also 12 v, I can hook up the new ones in the same way. If the old batteries are 6V, then I need to change the connections from series to parallel.

Are there any appreciable differences between AGM battery types (given the same volt and amp rating)? For example, given the battery location and it's exposure to puddles, would it be better to get a marine battery?

And finally, is one brand considered better than another and/or is there a preferred retailer?

Thanks again!
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Old 06-13-2017, 03:29 PM   #4
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Quote:
Originally Posted by Phoebe3 View Post
Thanks. Just to be sure I understand:

A 12V 200A battery will run my devices longer than a 6V 200A battery, correct? If the amps are the same, is there any benefit to having 6V batteries besides price?
...

Thanks again!

Most of the DC appliances uses 12v (fans, lights, radios, etc).
The car cigarette lighter (DC outlet) is standardized to 12v for that reason.

If you have a 6v battery, it will not provide enough voltage to support those appliances.

You will need to get 2 batteries,
and connect them in SERIES.

By connecting the batteries in series, you add up the voltages.

2x6v 200A battery in series = ONE 12v 200A power source.





if you connect 2 batteries in PARALLEL,
the voltage stays the same, but you add up the amp hours.

eg.
2x6v 200A battery in parallel = ONE 6v 400A power source.
or
2x12v 200A battery in parallel = ONE 12v 400A power source.


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Old 06-13-2017, 03:35 PM   #5
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.

Your understanding in #1 and #2 is correct.


Most people use AGM now. THey are maintenance-free, and do not give out harmful gases.

No need for marine-grade battery, IMHO they are mostly the same.

Edit: You need deep-cycle battery .


Check Costco if you have a membership. They have a very good warranty.

.
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Old 06-13-2017, 04:27 PM   #6
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Wow! Thanks - that was really helpful!
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Old 06-13-2017, 04:33 PM   #7
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Wow! Thanks - that was really helpful!
You are welcome.



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Old 06-14-2017, 12:29 AM   #8
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Wow! Thanks - that was really helpful!
An additional measurement to take is the height clearance available. The height for 12 volt batteries is pretty standardized but some 6 volt deep cycle AGMs are taller.
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Old 06-14-2017, 01:04 AM   #9
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Thanks. I intend to get 12V now that I know that they will work and give me additional use. I don't know what it comes with because the Service Manager couldn't remember. (I caught him early on a Monday.) But since they are wet cell, I'm going to assume they are 12V and I can replace with the same, except I'll buy AGM...plus more amps, if the batteries will fit in the space allotted.
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Old 06-14-2017, 03:41 AM   #10
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Quote:
Originally Posted by Phoebe3 View Post
Thanks. I intend to get 12V now that I know that they will work and give me additional use. I don't know what it comes with because the Service Manager couldn't remember. (I caught him early on a Monday.) But since they are wet cell, I'm going to assume they are 12V and I can replace with the same, except I'll buy AGM...plus more amps, if the batteries will fit in the space allotted.
What is the make and model of the converter/battery charger in the coach you're considering?
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