AGM Battery Questions

[Phoebe3]

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.

[BBQ]

.

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.

[Phoebe3]

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!

[BBQ]

Originally Posted by Phoebe3

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.


.

[BBQ]

.

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.

.

[Phoebe3]

Wow! Thanks - that was really helpful!

[BBQ]

Originally Posted by Phoebe3

Wow! Thanks - that was really helpful!

You are welcome.

[cruising7388]

Originally Posted by Phoebe3

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.

[Phoebe3]

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.

[cruising7388]

Originally Posted by Phoebe3

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?

[Phoebe3]

I couldn't get the service manager to focus enough to tell me whether or not I could add any additional solar panels, whether the charger was a 3-stage, the size of the Truma water heater or the number of amps the batteries were rated for. In fact, he couldn't tell me if the side windows would open, if they were slider or awning or if they had screens.

At this point, I think I know more about the coach than he does.

Good Lord. Now that I think about it, maybe that's a sign...

I'll call a little later and ask about the charger. I really did catch him first thing on a Monday and some people just aren't great in the morning.

I'm looking at the Coachmen Crossfit on the Ford Transit chassis.

[BBQ]

Originally Posted by Phoebe3

I couldn't get the service manager to focus enough to tell me whether or not I could add any additional solar panels, whether the charger was a 3-stage, the size of the Truma water heater or the number of amps the batteries were rated for. In fact, he couldn't tell me if the side windows would open, if they were slider or awning or if they had screens.

At this point, I think I know more about the coach than he does.

Good Lord. Now that I think about it, maybe that's a sign...

I'll call a little later and ask about the charger. I really did catch him first thing on a Monday and some people just aren't great in the morning.

I'm looking at the Coachmen Crossfit on the Ford Transit chassis.

Is this a new RV?

You do not have to worry about the battery yet... they last at least 5 yrs.
Many people have 10 yrs old wet cells.

[Phoebe3]

Yes, it is new, but I'm trying to predict how long I can be away from shore power. Without knowing the rating on the wet cells, I'm considering whether I should replace them right away with more amps.

Since I'm coming from a place of near total ignorance, I wanted to be prepared to replace the batteries , if needed.

The nearest one of these units to me is about 500 miles and I want to be pretty sure that's what I'm looking for before getting on a plane.

Also, the info in the online owner's manual says that one should check the fluid level in the wet cells periodically. If they are mounted under the coach and I have to see in the top in order to check that level, I will have to drop them. If they are the size of a car battery, that isn't going to happen. I'm not bragging when I say it would be impossible for me to lift 30 pounds while lying under a coach. And it's unreasonable for me to take it into a shop to pay someone else do it.

[BBQ]

.

Are you sure the new Coachman comes with wet cells?
And that the batteries are underneath the chassis?

I doubt they would put a wet cell in an inaccessible location.

[Davydd]

It's more like 50 lbs each and if wet cell you will have to check them frequently. You also mention 12v 200a batteries. I seriously doubt that. It is more like 2 batteries about 100a each for a total of 200a if that. Their literature doesn't say a thing about them but if they are as cheap to continue with wet cell batteries I would guess they would be as cheap and minimum in putting them in.

[Phoebe3]

Coachmen confirmed they are wet cell on the Crossfit, but said they are considering changing to AGM. I looked at all the pictures online and can't find the location of the batteries but I assume they are under the coach. I have found pictures under the coach that show the spare tire, generator and propane tank, but no batteries.

Inside, there are two bench seats in the back, but the fresh water tank is under one and the other contains the Truma water heater and the converter - no batteries that I can see. Views looking in the open back doors do not show batteries under the false floor, but perhaps they are tucked farther in so not immediately visible.

The front passenger seat swivels, but the driver's seat doesn't so they might possibly be under there.

It's a mystery. I KNOW they are there somewhere...

[cruising7388]

Originally Posted by Phoebe3

The front passenger seat swivels, but the driver's seat doesn't so they might possibly be under there.

If memory serves, the driver seat on the Transit doesn't swivel because of interference with the hand brake. I think Ford indicated that they were going to change the brake to permit driver seat swiveling but I don't know if the change was ever made. Check with Ford to see if this was done for the 2017/2018 chassis.

[Phoebe3]

Would be nice if both seats swiveled. I'm a Lark who is married to an Owl so the idea is that we will set up a table up front where DH can work on his computer after my lights have gone out. The passenger seat swivels for sure so we have that covered, but having both do it would be better.

[Davydd]

The M-B Sprinter van employs a "folding" hand brake in that you pull it up to set the brake and then return it down so the driver's seat can swivel. You pull it back up to release it.