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We are saddened to announce the passing of Gary Bunzer on April 17, 2020. We hope the RV Doctor website will continue to provide helpful information for you. Thank you for your interest and support for the RV Doctor - Debbie, Heather and Gretchen

Thursday, February 17, 2011

AGM Batteries for Motorhome

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 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. Also, we enjoyed your TV show. Any chance of hosting another one? Jon, (no city/state)

My comment Jon, (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 on-board as possible, regardless of battery type. But I can just as easily argue for wet-cell technology as well.

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. 

Thanks for the comments regarding the television show. Currently we are ready to go with a brand new TV show, but we are awaiting sponsorships from the manufacturers and campgrounds. I’m thinking it will be a long wait, given the state of the industry right now. But we are set to go as soon as the advertising dollars can be raised. 



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