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Old 12-06-2019, 03:32 PM   #1
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AGM battery replacement and converter

My el cheapo Costco flooded batteries are toast. I canít currently justify / afford lithium (and subsequent controller replacement).

Iím thinking about upgrading to AGM. From the reading Iíve done on the inter web, AGM is a better choice than flooded.

If I replace with AGM will my WF98xx controller be able to charge and maintain them? I ask because I talked to Battle Born and the lady said that if I went w lithium, the WF98xx wouldnít fully charge lithium.

Thoughts?
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Old 12-06-2019, 04:05 PM   #2
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AGMs

I can add that when we had our 24.1 Axis, we changed the two stock house batteries for two Lifeline AGM batteries. Nothing else was needed and they worked well for us.
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Old 12-06-2019, 04:11 PM   #3
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Originally Posted by WearyTraveler View Post

If I replace with AGM will my WF98xx controller be able to charge and maintain them? I ask because I talked to Battle Born and the lady said that if I went w lithium, the WF98xx wouldnít fully charge lithium.

Thoughts?
AGM batteries are still lead/acid chemistry batteries. There is a slight difference in the absorption voltage recommended for some types of AGMs, but it only effects the last 4% of the charge. The bulk and float charging voltages are the same for flooded and AGM.
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Old 12-06-2019, 04:39 PM   #4
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My thought ....

ďBetterĒ is subjective. Other than not having to water, and reduce corrosion in area of battery, what do AGM batteries provide for you? Flooded are cheaper and can be better value per Amp-hour if comparing similar quality.

On new installations/designs AGM offer more location options, but on an existing motorhome originally designed for flooded, Iím not sure AGM add as much value.

Also, did Costco batteries fail due to being ďcheapoĒ, or possibly something else? How long did original last? The motorhome isnít that old to have gone through two sets of batteries unless original batteries were damaged before delivery.
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Old 12-06-2019, 06:37 PM   #5
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Originally Posted by Chance View Post
ďBetterĒ is subjective. Other than not having to water, and reduce corrosion in area of battery, what do AGM batteries provide for you? Flooded are cheaper and can be better value per Amp-hour if comparing similar quality.

On new installations/designs AGM offer more location options, but on an existing motorhome originally designed for flooded, Iím not sure AGM add as much value.

Also, did Costco batteries fail due to being ďcheapoĒ, or possibly something else? How long did original last? The motorhome isnít that old to have gone through two sets of batteries unless original batteries were damaged before delivery.
Not sure about the original batteries. The current ones are 14 months old. Iíll ASSume that the previous owner never checked their levels because the wiring was zip tied and I had to remove ties and move cabling just to get the caps off.
He also kept it plugged in so he probably never worried about checking.
I donít know...
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Old 12-06-2019, 07:12 PM   #6
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True deep-cycle flooded batteries should last much longer than that if maintained properly and not discharged too deeply. I had no issue with my flooded house battery on Class C, and know of others over 5 years old. For van application a flooded isnít as practical because they are normally installed under floor where they canít be reached as easily.

Depending on manufacturer, the number of life cycles for flooded can be as high or higher than for AGM, so I wouldnít expect a longer life just due to it being AGM. For convenience, no doubt AGM wins, but it comes at a higher cost.

Costco may warranty your batteries (at least partially) so if you havenít tried that already, it may be worth a shot.

My biggest concern would be that if batteries met an early death due to some unknown cause, that the same thing could happen to the more expensive AGMs. However, it sounds to me based on your observation that they were probably not watered properly, or at all.
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Old 12-06-2019, 08:24 PM   #7
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[QUOTE=Chance;214703]ďBetterĒ is subjective. Other than not having to water, and reduce corrosion in area of battery, what do AGM batteries provide for you? Flooded are cheaper and can be better value per Amp-hour if comparing similar quality. QUOTE] AGMs have a faster charge rate because of their very low resistance, and thus heat up less than flooded batteries when charging. AGMs self-discharge rate is 20 times less than flooded batteries. That means if stored fully charged for 6 months, they would still retain 95% of the original charge. Because of their plate design, they can stand much more abuse (vibration, physical shock, heat) than even flooded deep cycle batteries can stand. Flooded deep cycle batteries have an RV service life of 4 to 6 years; where as, AGM batteries service life is 5 to 12 years. AGM batteries ONLY disadvantage is the price.
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Old 12-06-2019, 09:01 PM   #8
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.....cut.... AGM batteries ONLY disadvantage is the price.
Agree, but to me thatís a major difference, otherwise itís like comparing a $1,000 solar system to one that costs $2,000. I expect most things that cost more to perform better (although itís not always the case). The question is whether itís worth the difference to the particular buyer.

If we compare based on similar price because there is a limited budget, then you can get more capacity with flooded. If we compare 100 Ah of AGM to 160 Ah of flooded, the choice isnít as simple (at least to me).

By the way, Iíve seen data for lithium batteries having a very low self discharge rate, but nothing to suggest AGM is only 1% a month. Are you sure thatís correct?
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Old 12-06-2019, 11:57 PM   #9
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I love my AGM's. They are better than the OEM's in every way (expect Price). They discharge (when stored) at a very low rate. I have read this "1% per a month" many times on websites. That sounds about right for mine as well. Even it it was double ("2%") I would be happy. My Axis is in a insulated storge building and I dont even bother charging them. I just drive the RV once a month to exercise the engine and the Genny. If im tinkering with it at home I will plug it in for the day (30 amp) but mostly so I can have the lights and radio on sometimes run the AC or electic heater).

The OEM batteries would be almost dead in 2 or 3 weeks If I didnt charge them once a week....so im very happy with my AGM's.
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Old 12-07-2019, 09:11 PM   #10
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Originally Posted by Chance View Post
By the way, I’ve seen data for lithium batteries having a very low self discharge rate, but nothing to suggest AGM is only 1% a month. Are you sure that’s correct?
From the Concord Battery's website
AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries.
The reason for the percentage variance is temperature. For flooded batteries the rate of self-discharge at 104 F degrees is three times greater than the self-discharge at 68 F degrees and so it is with AGMs. It is all about a chemical reaction - the hotter the electrolyte the faster the chemical reaction occurs.
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Old 12-07-2019, 10:01 PM   #11
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I agree that AGM self discharges slower than flooded, but I was questioning the 1% per month, or 95% capacity after 6 months. Both seem too optimistic in normal use. Regardless, itís only important if it applies to the owner. For me, itís not a benefit I would spend more cash to buy because I use RVs too often.
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Old 12-08-2019, 12:35 AM   #12
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We plan to rarely boondock, so weíll normally be on shore power somewhere, even in the yard.

Would this negate the benefit of slow discharge rate of the AGM batteries?

And come to think of it - if I check the water level frequently, then flooded wouldnít be that bad?
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Old 12-08-2019, 04:59 PM   #13
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Changing to AGM's has been the only upgrade done and needed to the Tuscany in 5 years. The AGM's not only hold charge longer but you don't have to clean and replace cables and not having corrosion in the compartment is worth something.

You are going to spend a bit over twice but save money in the long term if you plan on keeping a Coach for 5 years or longer.

All my newer Fords have came with AGM's for a reason.
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