AGM batteries

ram22

Well-known member
Upgraded my North Trail to AGM batteries from CostCo for $400! I was replacing them in the campground, but CostCo assured me they were fully charged and ready to plug and play. They both went dead and the heater stopped working the first night! When I got home and put my charger on 2amps it went to zero quickly and auto shut off. Maybe they were fully charged after towing 8 hours, but I won’t know until my next dry camping weekend. Did I make a mistake buying AGM batteries?


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danemayer

Well-known member
Hi ram22,

If you had 2 batteries that were carrying a nearly full charge from the store, I'd expect that would be enough to run your furnace for one night without shore power. And if they were dead, I'm not sure towing for 8 hours would bring them back to a full charge.

Before your next trip, you might want to get them load tested at an auto parts store or repair shop.
 

Flick

Well-known member
Upgraded my North Trail to AGM batteries from CostCo for $400! I was replacing them in the campground, but CostCo assured me they were fully charged and ready to plug and play. They both went dead and the heater stopped working the first night! When I got home and put my charger on 2amps it went to zero quickly and auto shut off. Maybe they were fully charged after towing 8 hours, but I won’t know until my next dry camping weekend. Did I make a mistake buying AGM batteries?


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Generally, most new batteries are fully charged when manufactured and depending on how long they have sat on the store shelf, may only have a token charge left when purchased. It is advisable to recharge new batteries with a charger before extended use. As we know, driving your vehicle with new batteries charges them up also.
Driving your vehicle for 8 hours certainly would top off undercharged vehicle batteries, but agreeing with Dan, I’m not sure a bank of batteries in an RV would receive a near full charge when dead, from the truck charging system. Getting them load tested is advisable.
Check to be sure you have a good battery to battery connection and for some reason either battery is not pulling its share of the load thru a bad connection. You may want to disconnect the batteries and using a simple voltage meter, check voltage against each other.
The AGM’s are a very good choice in that they’re maintenance free.
 

wdk450

Well-known member
I would wonder if 1 or more of the batteries were new defective.

From my electronic troubleshooting days, I would then ask: "What was changed?" That would be what you changed while doing the battery swap - the wiring. Could you have possibly installed one of the batteries with the polarity reversed? As advised before you need to troubleshoot this with a DC voltmeter before you try to go out camping again. If you can't move the trailer to somewhere where you have shore power (a household 15 amp circuit should be enough for just the battery charger/converter) maybe you can borrow or rent a generator to take to your storage place.

BTW, if you had a big 5th wheel like a lot of us on the forum, you wouldn't have even gotten hitched up to go out, as the 12 volts DC is used on the heavy lift landing gear motor. Also, be aware that a good working 12 volts battery system is ESSENTIAL to the trailer emergency braking on towing disconnect system, although I am not sure that bumper tow trailers have this.
 

Oregon_Camper

Well-known member
How cold was it at night? what was the low temp? You get into mid to low 30's (and below) you will surly encounter the Peukert effect. That will have a HUGE impact on your batteries ability to output power.

Once the temp go back up, the Peukert effect starts to go away and it appears the batteries are fully charged.
 

ram22

Well-known member
I confirmed my suspicion with a visit to the local Interstate Battery distributor. AGM battery approximately 4 amp-hours less output than equivalent lead-acid RV battery. That’s 8 amp-hours less in my two battery North Trail. The benefits are no maintenance plus better tolerance to vibration and bumpy roads. I might be returning my AGM batteries to CostCo. They were $200 each before core refund.


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Flick

Well-known member
I confirmed my suspicion with a visit to the local Interstate Battery distributor. AGM battery approximately 4 amp-hours less output than equivalent lead-acid RV battery. That’s 8 amp-hours less in my two battery North Trail. The benefits are no maintenance plus better tolerance to vibration and bumpy roads. I might be returning my AGM batteries to CostCo. They were $200 each before core refund.


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I’m sorry that you’re having all the problems with your batteries. Replacing batteries should be a pretty straight forward process.
Not knowing what amp hour your AGM batteries are rated at, even if what Interstate told you is correct and I have no reason to doubt them, you’re only talking less than 5% of your AHs if they are 100.
If you take them back, and I’m sure you know this, but for the sake of others, be sure to get some form of deep cell battery that can withstand the deep discharges that RV batteries can go thru.
Have you thought about a solar trickle charger to help the charge level when camping? Have a nice day.
 

Oregon_Camper

Well-known member
I confirmed my suspicion with a visit to the local Interstate Battery distributor. AGM battery approximately 4 amp-hours less output than equivalent lead-acid RV battery. That’s 8 amp-hours less in my two battery North Trail. The benefits are no maintenance plus better tolerance to vibration and bumpy roads. I might be returning my AGM batteries to CostCo. They were $200 each before core refund.

[FONT=Roboto, arial, sans-serif]Absorbed Glass Mat (AGM) batteries are lead acid batteries. Did they mean "flooded" vs "AGM" (both are lead acid)? If you really want performance, have you considered Lithium? Be prepared..they are not cheap. 100amp hour battery is ~$950....but there are a lot of benefits with Lithium over Lead Acid. [/FONT]
 

ram22

Well-known member
Oregon Camper, you are correct, the old batteries are flooded lead acid and new are AGM. But, loss of ah worse than I posted above! New AGM battery placarded 70ah and I called Interstate with the Fitment Code and Group and CCA of old battery and it is 81ah! Old battery had more than 15% more amp hours than AGM!
Flick, solar panel is good idea. The old batteries are Marine/RV.
Considering the substantially lower amp-hours for these AGM batteries, I am even less enthralled with them!


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porthole

Retired
Upgraded my North Trail to AGM batteries from CostCo for $400! I was replacing them in the campground, but CostCo assured me they were fully charged and ready to plug and play. They both went dead and the heater stopped working the first night! When I got home and put my charger on 2amps it went to zero quickly and auto shut off. Maybe they were fully charged after towing 8 hours, but I won’t know until my next dry camping weekend. Did I make a mistake buying AGM batteries?


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What were the batteries you bought? Deep cycle or starting batteries?
Did you replace the batteries with equal or greater capacity than the originals?
Did you check the voltage before installing? After installing? Were you plugged in and using the onboard converter?


If your batteries were dead when you left camp, towing for 8 eight more than likely did not fully charge them.


Peukert's law is only an approximation and does not take temp into account, or the age of the battery, it does require a 'constant' in the formula depending on the type of battery since multiple battery types of today were not in existence 100+ years ago.


If the new batteries are equal to or greater in capacity then the batteries that came with your RV, and you were able to get longer run times with the old set, skip the equation and get the batteries properly fully charged and load tested.
 

ram22

Well-known member
What were the batteries you bought? Deep cycle or starting batteries?
Did you replace the batteries with equal or greater capacity than the originals?
Did you check the voltage before installing? After installing? Were you plugged in and using the onboard converter?


If your batteries were dead when you left camp, towing for 8 eight more than likely did not fully charge them.


Peukert's law is only an approximation and does not take temp into account, or the age of the battery, it does require a 'constant' in the formula depending on the type of battery since multiple battery types of today were not in existence 100+ years ago.


If the new batteries are equal to or greater in capacity then the batteries that came with your RV, and you were able to get longer run times with the old set, skip the equation and get the batteries properly fully charged and load tested.

I bought AGM to replace flooded lead acid with exact same fitment code to fit in my battery boxes. When I returned the AGM yesterday, I asked CostCo Auto to show me the ah rating of the flooded lead acid. The AGM were placarded 70ah. Their catalogue has dashes in place of ah value for flooded lead acid and only shows value for AGM! The local Interstate Battery Distributor told me they were 81ah. They took the AGM back and I am replacing exact same flooded lead acid battery and CostCo gave me $204 cash refund! Any more questions? Lol
f2fb40c4c86ddd660143747a3d257324.jpg



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wdk450

Well-known member
I bought 2 Group 24 AGM's from a powered wheelchair refurbisher in Sacramento 5 years ago, about $79 each as I recall. I found the ad on Craigslist, and I have seen other ads there for used solar panel system AGM batteries. Coupled with the 4 stage Progressive 9200 series charger/converter (with the daily desulphation stage) these batteries continue to serve me well.
 

Flick

Well-known member
I bought AGM to replace flooded lead acid with exact same fitment code to fit in my battery boxes. When I returned the AGM yesterday, I asked CostCo Auto to show me the ah rating of the flooded lead acid. The AGM were placarded 70ah. Their catalogue has dashes in place of ah value for flooded lead acid and only shows value for AGM! The local Interstate Battery Distributor told me they were 81ah. They took the AGM back and I am replacing exact same flooded lead acid battery and CostCo gave me $204 cash refund! Any more questions? Lol
f2fb40c4c86ddd660143747a3d257324.jpg



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Good job! All that is well, ends well. And the gentleman rides off into the sunset with his head held high. Lol.
 
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