Wednesday, February 8, 2023


Advantages of AGM batteries in motorhome


gary-736Dear Gary,
I’m thinking my coach batteries may need replacing within the year. I asked my RV dealer whether AGM batteries are a good idea. Currently it has the older flooded-cell type that came from the factory (two chassis batteries and three house batteries). The answer I got from my dealer was to stick with the technology it came with and not switch to AGMs. Just so you know, I have a 2004 motorhome with a three-stage charger. I’d be interested in your comments and advice. —Jon

Dear Jon,
My comment (since you asked) is that I’m guessing your dealer does not sell AGM batteries but does sell flooded, wet-cell batteries. My advice? Well, I’m a strong proponent of the AGM technology. And since today’s motorhomes are so DC voltage dependent, I’m also in favor of having as much DC current onboard as possible, regardless of battery type. But I can just as easily argue for wet-cell technology.

Here are some arguments for switching to AGM batteries. First, they are highly resistant to vibration and shock; a plus for RV applications when you consider the jostling and bouncing the motorhome does on the road. Their recombinant gases are effective to about 99%. What this means is that the hydrogen and oxygen are recombined inside the battery safely within each cell. Ever notice the bubbling and off-gassing of a lead-acid battery while under a severe charge? Most AGM batteries vent hydrogen vapors at less than 2%, where 4.1% is needed to support flammability in air.

The inherently low internal resistance of an AGM battery is another welcomed benefit to RVers who store their motorhomes part of the year. According to one maker, during storage, the self-discharge rate of an AGM battery is 3 to 10 times better than a gel battery and almost 50 times better than a typical flooded lead-acid battery. The reason is because the electrolyte is not liquefied, but rather absorbed into a floss-like glass matting. AGM batteries also deliver and receive current much faster and at the higher rates available today. Your three-stage charger will suffice nicely and adapt well for AGM batteries. As an example, AGM batteries can be charged 10 times faster than a same-rated gel battery and 5 times as fast as a like-sized flooded lead acid battery.

Because AGM battery technology permits more positive plate material to be saturated by the absorbed mats in each cell, there is an automatic increase in the battery’s capacity in virtually every area. More life cycles, reduced internal resistances, higher amp-hour rating in some cases, more reserve capacity and deeper depth of discharge cycles are some of the improvements over other types of sealed, lead-oxide batteries.

Yeah, I like ‘em! So if your wallet can endure and you consider yourself a “serious” RVer, then I’d truly consider the upgrade when it’s time to replace your existing batteries. 

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.



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2 years ago

What is a “serious” rver?  Sounds like this dude is getting kickbacks from AGM manafactures. Too bad.

William Statt
4 years ago

Do you have to change the charging system when switching to an AGM battery in an RV. Will the normal charging system overcharge it?

Jerry heiser
5 years ago

Gary. I currently use 4. 6volt wet cell batteries. Considering switching to agm would it be better to go with 4. 6 volt agm over 2 12 volt agm

Patrick Granahan
5 years ago

Just a comment on the cost of AGM batteries.

Look to Amazon for the best prices.
Because these are sealed units the can be delivered
to you via FedEX or UPS.
Liquid acid batteries cannot be delivered.

My current 12 volt AGM 100AH battery came from
Amazon @ about $150.
These batteries (Universal Batteries from Texas distributor via Amazon)are very very heavy !!!

5 years ago

I just bought a TT and asked about an AGM upgrade. They would do it for an additional $299. Essentially they were giving me no credit for the deep cycle provided free and just selling me an AGM. I decided to take the free non-AGM but would replace it in a year or so. I just know I am going to forget to check water levels.

5 years ago

Hi Matt,

Thanks for the reply, I guess my question should be: If I buy AGM’s is it necessary to replace my single stage charger too? This combined with a battery upgrade could be many hundreds of dollars. For that, I think I could remain with lead acid batteries for a long time. They are a proven and dependable source of power…and there’s no learning curve or big wallet required- JMHO

5 years ago

If your unit has a charger that can change to the proper charging ratio then you can change to any battery type. If you don’t know how to switch the ratio on the charger or it’s not changeable then you must stay with the type of battery issued from the factory no matter what wonderful attributes the different battery types have. Each battery type has its own different charging profile, and charging them with the wrong profile can shorten their lives. I have ran an electric car with a changeable Delta-Q charger capable of changing the profile to wet, gel, AGM and even lithium type batteries. If your talking AGM then maybe you should consider lithium. Be careful of what you hear from your battery dealer. Check with your battery manufacturer.

Patrick J Granahan
5 years ago

I too am a big fan of AGM batteries. Alter reading all the facts I went with AGM and have been very pleased.
My local RV dealer’s service did not even know what a AGM was and questioned what I had installed..
I would never go back to the old liquid acid batteries !

Matthew Colie
5 years ago

I used to do a lot of DC power upgrades to performance cruisers. (These are retired racing sailboats.) I always suggested that everything be changed to AGM. Sometimes there was a cost issue, but when I told the owner that we could then hide the bank(s) as they would require no maintenance, that usually sold it. Many came back to thank me for that change.

Lee Ensminger
5 years ago

Gary, I completely agree. I just replaced our 8 wet cell golf car batteries with two 8 D AGM batteries. Placing 8 outgassing wet cell batteries in a sealed compartment was stupid. Access for checking and watering was ridiculous. Half of the wiring had to be disconnected to check them. Then there’s the corrosion from the gases! Now, my wiring is greatly simplified, and no mess. Too early to tell how this will hold up long-term, but I’m liking it so far!

5 years ago

What if you only have a single stage charger as part of your converter/charger unit? The charging voltage on most of these is between 13 and 13.7 volts typically.

Matt Colie
5 years ago
Reply to  Drew

If that is your situation, upgrade the charger to one that is capable of managing an AGM.

5 years ago
Reply to  Drew

Single stage chargers destroy ALL battery types over time. It will destroy your standard flooded batteries as well.

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