AGM Batteries

[Schiefswret]

I’m going to switch from OEM batteries to AGM. We are always on campground shore power and have no solar, our electrical system has no aftermarket add on’s or changes to it as our current camping style does not include any boondocking. When choosing an AGM battery, in our situation, is the Ah rating of the battery of any particular importance and if so or if not, why?
All inputs very much appreciated. TY

[Cate&Rob]

is the Ah rating of the battery of any particular importance and if so or if not, why?

Hi Dave & Sue,

The Ah rating of the battery is the most important number to consider. (other than making sure that the size you choose will fit in your battery box) This is the measure of how much energy the battery can store. You will find "deep cycle" and "deep cycle / starting" batteries. The deep cycle will usually have slightly more Ah capacity and is the one you want for RV application. Remember that you can only use 50% of the stated capacity without risking damage to the battery, whether wet cell or AGM.

Rob

[Schiefswret]

TY Rob. I was hoping that was not the case, as it appears that the costs increases pretty much as the Ah increases 😩. I guess you get what you pay for. In the AGM world of batteries, is there a make/model that you would recommend? Thanks again.

[TucsonJim]

Dave & Sue. In your specific case, the Ah rating is not a huge factor. If you aren't boon docking, and you are almost always plugged into shore power, you can probably get by with a relatively low Ah rating. For typical usage, I'd look for an Ah rating of about 90 (at a 20 hour rate). This will provide plenty of power to run things like lights and your break away brakes in an emergency while towing. It will also allow you to extend and retract the landing gear and slide rooms a few times before the battery starts to be depleted.

A good point of reference for battery usage is how many amp hours you can use before the battery is depleted and needs recharging.

On a flooded (lead/acid) battery, you can use up to 50% of the capacity - So a 90 amp hour battery will yield 45 useable amp hours.
An AGM battery can be depleted approximately 70% - Yield is 63 amp hours on a 90 amp hour battery.
And a lithium iron phosphate (LiFePO4) battery can yield approximately 95-100%.

Jim

[Schiefswret]

Jim, much thanks. I've had my eye on a few models in the 60-100 Ah area. I've been running two batteries since the purchase of our current rig and other than setting and breaking camp I'm seldom if ever in need of battery only power. I have 30amp service at my house so it seems to me that 70-100 Ah will suffice nicely for my particular situation but it always pays to check with you more experienced RV dudes. thanks again.

[TucsonJim]

Jim, much thanks. I've had my eye on a few models in the 60-100 Ah area. I've been running two batteries since the purchase of our current rig and other than setting and breaking camp I'm seldom if ever in need of battery only power. I have 30amp service at my house so it seems to me that 70-100 Ah will suffice nicely for my particular situation but it always pays to check with you more experienced RV dudes. thanks again.

You're very welcome. And if you're running two 12V batteries in parallel, you could easily get by with two 60 amp batteries. That would give you 120 total amp hours x 70% or 84 amp hours of useable power before needing to recharge.

Jim

[Cate&Rob]

Schiefswret
Hi Dave & Sue,

I defer toTucsonJim Jim’s better understanding of the discharge capability of AGM vs the wet cell batteries that I am more familiar with. Considering that your usage is as minimal as you describe, why are you changing from (inexpensive) wet cell batteries to the (considerably more expensive) AGMs?

Rob

[Schiefswret]

Rob, the reason is that I'm getting too lazy to, every thirty days, to do the PM necessary and would rather just change to AGM and be done with it, however, I'm admitting is only due to my laziness. After 2+ years of monthly battery PM I'd rather save my energy for some other PM efforts in the RV.

[Cate&Rob]

Schiefswret
Just an observation . . . If you are adding water to your batteries every month, your battery discharge is much greater than you think. Our RV battery usage is similar to what you describe and although I check the batteries every few months, I almost never add water. By comparison, I have a boat and a golf cart that each use battery power much more extensively. I add a lot of water to those batteries .

Rob

[TucsonJim]

Schiefswret
Just an observation . . . If you are adding water to your batteries every month, your battery discharge is much greater than you think. Our RV battery usage is similar to what you describe and although I check the batteries every few months, I almost never add water. By comparison, I have a boat and a golf cart that each use battery power much more extensively. I add a lot of water to those batteries .

Rob

Yeah, I was a little surprised when I serviced my son's Interstate lead/acid RV batteries yesterday. He just moved to Arizona from Utah for a new job and I'm doing some errands for him. I pulled the batteries and he said he hadn't added water in probably six months. When I checked, they were full. No water needed. It was also interesting to me that the batteries were three years old and when I checked them with a hydrometer, they were still in pretty good shape.

Jim

[Guest]

Overfilling maybe? Batteries that are overfilled will purge out the extra fluid.

Jim