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Old 10-15-2020, 02:43 PM   #1
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Flooded Lead Acid vs AGM Batteries

A stupid question:
If there is no "vent" on a battery: is it safe to assume that it is an AGM battery?
I've got what looks like caps on mine; but no vent lines...
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Old 10-15-2020, 02:56 PM   #2
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Not a safe assumption. Remember the "sealed maintenance free" batteries? FLA and really no caps but you could pry the center strip up to get to the cells.



AGM battery makers are pretty proud of their batteries (can you tell by the price?) and usually have AGM badging prominently displayed on them.
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Old 10-15-2020, 03:34 PM   #3
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Virtually all automotive batteries are sealed lead acid (SLA) types with no filler caps. These are absolutely certain to not be true deep cycle batteries. I doubt you will find an amp hours spec for one of these. Some manufacturers are starting to deliver cars with AGMs (absorbed glass mat) though and these have no filler caps.

This might be a good time to segue into real deep cycle batteries vs pretenders. Real deep cycle FLAs (flooded lead acid as opposed to AGMs and the only inexpensive ones are 6V golf cart batteries), have filler caps, more room above and below the plates for electrolyte and thicker plates. Each are important for long term deep cycle use.

AGM batteries for the most part can be used in deep cycle service because as best I can tell, there is limited difference in AGMs advertised for deep cycle use and run of the mill AGM batteries. Another RV forum member once noted that one brand which differentiated deep cycle from starting models had a heavier battery weight for their deep cycle version. That indicates more lead and heavier plates which is the one characteristic of FLA deep cycle batteries that is important for AGMs in deep cycle use. But I think that the way AGMs are built minimizes lead plate losses during deep cycle use.

AGMs do not require checking electrolyte levels and can be mounted in any position. They and FLAs experience shorter life if discharged below 50% although some believe that AGMs can go lower. Don't know for sure as I have never seen any data for AGMs.

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Old 10-15-2020, 03:38 PM   #4
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Thanks. I just got tripped up by the apparent lack of vents; so I figured that it would be safer to just ask.
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Old 10-15-2020, 04:19 PM   #5
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Originally Posted by Bob Denman View Post
Thanks. I just got tripped up by the apparent lack of vents; so I figured that it would be safer to just ask.
AGM batteries are just a particular battery type of a category of batteries known as valve regulated lead acid batteries (VRLA).

A little deeper explanation - lead paste grid used in batteries is weak and would soon fall to the bottom of the batteries if it was not made of a alloy to make grids stronger. The common alloying metals are tin, calcium, antimony and selenium. Each alloying element does strength the lead grid, but also imparts some different characteristics to the batteries operation. When calcium is used to strengthen the grids the batteries out-gas little water when recharging. This means they can be sealed for normal operation. To prevent explosion when overcharged, overheated or when taken to high altitude there is a valve to regulate the battery's internal pressure. The batteries are commonly known as VRLA batteries. When the lead-calcium grids are are separated by glass mats filled with filled sulfuric acid they are known as AGM batteries but still are VRLA batteries.
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Old 10-15-2020, 04:22 PM   #6
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Thanks for the education.
Now: my head hurts!

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Old 10-15-2020, 04:43 PM   #7
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Originally Posted by DavidEM View Post

This might be a good time to segue into real deep cycle batteries vs pretenders. Real deep cycle FLAs (flooded lead acid as opposed to AGMs and the only inexpensive ones are 6V golf cart batteries), have filler caps, more room above and below the plates for electrolyte and thicker plates. Each are important for long term deep cycle use.

AGM batteries for the most part can be used in deep cycle service because as best I can tell, there is limited difference in AGMs advertised for deep cycle use and run of the mill AGM batteries. Another RV forum member once noted that one brand which differentiated deep cycle from starting models had a heavier battery weight for their deep cycle version. That indicates more lead and heavier plates which is the one characteristic of FLA deep cycle batteries that is important for AGMs in deep cycle use. But I think that the way AGMs are built minimizes lead plate losses during deep cycle use.

AGMs do not require checking electrolyte levels and can be mounted in any position. They and FLAs experience shorter life if discharged below 50% although some believe that AGMs can go lower. Don't know for sure as I have never seen any data for AGMs.

David
Excellent dissertation but here is some more facts.


!. Lead-antimony batteries can be deep cycled more times than lead-calcium batteries.
2. Lead-antimony flooded batteries require more frequency maintenance as they near end of life (water and equalization).

3. Lead-calcium batteries have lower self-discharge rates and will draw less current when on float than lead-antimony batteries.
4. Lead-calcium positive grids grow in length and width when overcharged. Over long periods this can lead to case rupture (higher than required float voltage).
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Old 10-15-2020, 04:50 PM   #8
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So after taking another look at the caps on my batteries: they can be removed...
I will replace them with a pair of AGM batteries once they "hit the wall"...
Any advice as to brand?

These are 27s; I'll think I'll get 31s the next time.

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Old 10-15-2020, 06:03 PM   #9
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Looks like they are also due for a little cleaning up before installing them. If you plan on keeping them, I would recommend adding the Flo-Rite Water System to make it easier to keep the water levels up.

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Old 10-15-2020, 06:38 PM   #10
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Yeah... I had just pulled them out of the rig.
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Old 10-15-2020, 07:16 PM   #11
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I am on 2 years now with the 4 T105 AGM's I installed in the Tuscany. They have held voltage and allowed me to overnight with heat and fridge and other small loads and still having enough power to brew coffee prior to generator time

Worth the money just to get rid of the corrosion but I am a heavy battery user in that we tend to cold weather camp more than hot and when we boondock we need heat all night long. If somone is a light user then you wont have the gassing off issue as bad and may be harder to justify the 3x cost.

Not having to deal with corroded cables and terminals plus the carbon steel corrosion in the compartment is enough for me to upgrade.
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Old 10-15-2020, 07:26 PM   #12
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I've always had faith in Trojans..
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Old 10-15-2020, 07:59 PM   #13
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Originally Posted by lwmcguire View Post
I am on 2 years now with the 4 T105 AGM's I installed in the Tuscany. They have held voltage and allowed me to overnight with heat and fridge and other small loads and still having enough power to brew coffee prior to generator time

Worth the money just to get rid of the corrosion but I am a heavy battery user in that we tend to cold weather camp more than hot and when we boondock we need heat all night long. If somone is a light user then you wont have the gassing off issue as bad and may be harder to justify the 3x cost.
Not having to deal with corroded cables and terminals plus the carbon steel corrosion in the compartment is enough for me to upgrade.
My previous Class A used to AGM group 31 batteries for the house. My current class A used two group 29 FLA batteries for the house and one VRLA battery for starting. I also have a golf cart with 6 group GC-8_ FLA batteries. In my opinion, if you see corrosion anywhere, you are over filling the FLA batteries. Every manufacturer of FLA batteries warns - never add water to the batteries until they are fully charged (2.13 volts per cell resting at 70 F degrees). All LA battery's positive plates grow in length and width as they discharge and the water level will drop. This is why the case bulges when a LA battery is discharged. Topping FLA batteries off in the cool morning when the batteries are 50% discharged will result in one to two tea spoons of water being pushed out of the refill caps when the battery is warm and fully charged (bulk charging the LA flooded battery will cause the electrolyte to be heated into the 110 to 120 degrees). That is why the better chargers monitor battery temperature rather than assuming the batteries are at the same temperature as the charger.

That said, equalization (over charging the battery to produce hydrogen bubbles) will cause serious out-gassing; which in-turn, will cause corrosion. Clean-up and watering are necessary after equalization. Also as FLA batteries near the end of their useful life or abused, they tend to out-gas more during charging and thus can cause considerable corrosion.
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Old 10-15-2020, 09:43 PM   #14
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My previous Class A used to AGM group 31 batteries for the house. My current class A used two group 29 FLA batteries for the house and one VRLA battery for starting. I also have a golf cart with 6 group GC-8_ FLA batteries. In my opinion, if you see corrosion anywhere, you are over filling the FLA batteries. Every manufacturer of FLA batteries warns - never add water to the batteries until they are fully charged (2.13 volts per cell resting at 70 F degrees). All LA battery's positive plates grow in length and width as they discharge and the water level will drop. This is why the case bulges when a LA battery is discharged. Topping FLA batteries off in the cool morning when the batteries are 50% discharged will result in one to two tea spoons of water being pushed out of the refill caps when the battery is warm and fully charged (bulk charging the LA flooded battery will cause the electrolyte to be heated into the 110 to 120 degrees). That is why the better chargers monitor battery temperature rather than assuming the batteries are at the same temperature as the charger.

That said, equalization (over charging the battery to produce hydrogen bubbles) will cause serious out-gassing; which in-turn, will cause corrosion. Clean-up and watering are necessary after equalization. Also as FLA batteries near the end of their useful life or abused, they tend to out-gas more during charging and thus can cause considerable corrosion.
Don't disagree with anything you noted Beau388

Our coach sat for quite awhile due to DW health and some surgery so they were mistreated at the beginning and of course during the coach build and sitting on the lot waiting for delivery.

The batteries were about 3.5 years old when I exchanged them. The Magnum was set up correctly and the temperature compensator worked fine. We tend to draw the bank down and pushed it many times beyond 50% in order to have breakfast prior to the 7 or 8 am Generator times depending on where we were. We stay in many parks with no hookups but restrictions due to proximity.

Also used the mineral oil in two of the batteries to see if it reduced the off gassing but we still generated plenty of Hydrogen.

I have AGM or sealed in every toy and vehicle and will never ever go with flooded again. My GEM car has 6 12v AGM's and the old cart now has AGM as well.

The Coach batteries are two group 31 sealed batteries and still going strong after 5.5 years

Prior to retiring we had a significant amount of equipment on the Farms and Ranch with multiple batteries or large single batteries. Same deal they were all converted to either sealed or AGM to reduce maintenance. Out of all the equipment maybe 10% didn't have battery issues over time. Much of the equipment might run days in a row for 16 hours a day so the batteries got well used.

Safety was a big deal for us to keep the insurance cost down for the employees. Any type of accident or issue that got the attention of the insurance carriers always wound up in increased premiums. The battery maintenance usually went to a lower on the totem pole employee that may not always be careful as they should be or were trained to be.

The savings in battery life and man hours paid for the higher priced batteries in less than two years.

Our security systems all use AGM as well as little things like the stair chairs and so on. We went to AGM in the outdoors toys starting with the Jet Skis many many years ago. I won't ever have a flooded battery that isn't sealed if I can avoid it any way possible.

If a person don't mind the watering and checking then save the money and stay with flooded. If you like to just open the door and blow the compartment out with air and go do something else then AGM are the only way to go if you camp in cold weather.
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Old 10-15-2020, 10:31 PM   #15
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Again, I agree with what you posted lwmcquire. There is no best house battery type. It is a matter of use, convenience, cost and capacity. There are many Internet portals that list the advantages and disadvantages of the different types of batteries. Each battery type has several sub types and different manufactures of the sub types hype their differences. For instance is battery listed as marine/RV AGM (described as more rugged than an deep cycle RV battery) better than deep cycle labeled AGM (described as longer life)? Is the fact that a LiFePo4 battery cannot be charged when its temperature is below 32 F degrees important? If you are going to trade coaches every five years, do you need the "best" batteries?
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Old 10-16-2020, 10:34 AM   #16
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Again, I agree with what you posted lwmcquire. There is no best house battery type. It is a matter of use, convenience, cost and capacity. There are many Internet portals that list the advantages and disadvantages of the different types of batteries. Each battery type has several sub types and different manufactures of the sub types hype their differences. For instance is battery listed as marine/RV AGM (described as more rugged than an deep cycle RV battery) better than deep cycle labeled AGM (described as longer life)? Is the fact that a LiFePo4 battery cannot be charged when its temperature is below 32 F degrees important? If you are going to trade coaches every five years, do you need the "best" batteries?
Hey, since we're on the same page

Here's to some great camping and adventures in 2021 and beyond!
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Old 10-16-2020, 12:57 PM   #17
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Hey, since we're on the same page

Here's to some great camping and adventures in 2021 and beyond!
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Old 10-16-2020, 02:55 PM   #18
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There’s so much grey area in battery technology that it pays not to think in black and white terms.

Attached is an article comparing the effect of cold weather on AGM versus lithium batteries. While the comparison seems highly biased to make lithium look that much better, it does touch on the limitations of lead-based batteries when used in cold weather. And more importantly, how a fast discharge rate reduces AGM total energy capacity.

The comparison only goes to 80 Amps with 210 Amp-hours of battery capacity, which means about 1,000 Watts from two large group 31 deep-cycle AGM batteries. Even that drains them fast, and you’d need twice that (about 2,000 Watts) to power a microwave.

Ignoring the lithium data altogether, there’s much to consider regarding AGM batteries in cold weather and or fast discharge rates. Test is a little flawed and biased, but worth looking at in my opinion.


https://battlebornbatteries.com/lead...e-paper-study/
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Old 10-16-2020, 03:23 PM   #19
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Originally Posted by Chance View Post
There’s so much grey area in battery technology that it pays not to think in black and white terms.

Attached is an article comparing the effect of cold weather on AGM versus lithium batteries. While the comparison seems highly biased to make lithium look that much better, it does touch on the limitations of lead-based batteries when used in cold weather. And more importantly, how a fast discharge rate reduces AGM total energy capacity.

The comparison only goes to 80 Amps with 210 Amp-hours of battery capacity, which means about 1,000 Watts from two large group 31 deep-cycle AGM batteries. Even that drains them fast, and you’d need twice that (about 2,000 Watts) to power a microwave.

Ignoring the lithium data altogether, there’s much to consider regarding AGM batteries in cold weather and or fast discharge rates. Test is a little flawed and biased, but worth looking at in my opinion.


https://battlebornbatteries.com/lead...e-paper-study/
It has been noted before in this and other RV forums that the ion movement in AGM batteries in cold weather is really slow. It especially shows up in heavy currents and recombination during the absorption phase of recharging. Partly this can be caused because a lack of exothermic heat (low hysteresis) during the chemical reaction in AGM. Again this is all compared to the lead-antimony FLA battery which is the standard for efficiency and life in a completely reversible chemical reaction producing electricity.
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Old 10-16-2020, 04:11 PM   #20
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It has been noted before in this and other RV forums that the ion movement in AGM batteries in cold weather is really slow. It especially shows up in heavy currents and recombination during the absorption phase of recharging. Partly this can be caused because a lack of exothermic heat (low hysteresis) during the chemical reaction in AGM. Again this is all compared to the lead-antimony FLA battery which is the standard for efficiency and life in a completely reversible chemical reaction producing electricity.
That's why I store my RV at the end of October, and pick it up in April...
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