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Old 03-12-2019, 08:44   #1
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AGM batteries, PSOC and sulphation

I got a PM from a member regarding where does this belief that AGM’s need to be fully recharged more frequently than flooded batteries comes from.
Well the Lifeline manual alludes to it but doesn’t specifically point it out. But I ran across this article, which puts PSOC into perspective for AGM’s and capacity loss. I wish they had carried the testing further and regularly ran a conditioning / equalizing charge at least monthly. I believe this test really only covers one month, I’d want to know if capacity continues to drop at that rate or does it eventually level off?
https://www.practical-sailor.com/iss...s_11691-1.html
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Old 03-12-2019, 11:33   #2
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Re: AGM batteries, PSOC and sulphation

For those not aware, by our own Maine Sail.

Some more details here

https://marinehowto.com/how-fast-can...ery-be-charged

https://forums.sailboatowners.com/th...tteries.171123

Note MS does not state this specific issue, of PSOC causing sulfation, is limited to AGM, it is true for all lead.

Being in general less robust and requiring more precise care, AGM just shows a more obvious immediate impact very clearly in even a short period of time.
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Old 03-12-2019, 13:08   #3
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Re: AGM batteries, PSOC and sulphation

The question I have is, does AGM sulphate more than flooded or Gel?
Or does it nor recover as well from sulphation, or both?
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Old 03-12-2019, 14:29   #4
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Re: AGM batteries, PSOC and sulphation

Not sure how sulfation itself is quantified in order to answer that, without destroying the battery.

I think easier to measure the reduction in SoH% as a result of just that one abuse factor PSOC cycling, all other factors being longevity-optimized.

And would guess yes, AGM loses SoH more quickly as a result.

With the exception of Firefly Oasis of course.

iirc, Lifeline's ability to be equalized did not give any "recovery" advantage over Northstar or Odyssey.

I think best to see that as more of a preventative.
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Old 03-12-2019, 16:00   #5
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Re: AGM batteries, PSOC and sulphation

Well, we have a n=1 example that shows that persistent PSOC is not necessarily all that bad for our AGM batteries.

Our boat has 6x 110Ah Victron Energy AGM batteries (12V). They were installed by the previous owner in 2014, so are now almost 6 years old. In their entire history the boat has not been marina berthed nor had access to shore power other than short periods on the hard or at visiting marina berths.

Since we’ve owned the boat they’ve been drained to 15% SOC over a period of 3 months once (then charged to 100% over 2 days on a weak shore power connection) and regularly used in PSOC range 45% - 85%, getting to 100% SOC once or twice a fortnight.

As we’ve been upgrading our charging system we recently tested the batteries and they showed capacities of 103-107 Ah each. So, not too bad given the abuse they get.

Adding 1000W solar charging via MPPT regulators (currently 600W via PWM) shortly and 700Ah LiFePO4 batteries for the house bank next year, so just need the batteries to last another six months.
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Old 03-12-2019, 17:14   #6
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Re: AGM batteries, PSOC and sulphation

I don’t mean actual tear down and inspection but sulphation does of course degrade a batteries capacity. It also slows the speed at which it will accept a charge and causes a battery to take longer to charge, so it almost causes sulphation to increase as if charging stays the same the more sulphated a bank becomes the less it will be charged, causing more sulphation.

I just wonder if anyone has done any testing to determine the difference in capacity loss of AGM, vs Flooded, vs Gel in a PSOC situation
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Old 03-12-2019, 17:57   #7
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by john61ct View Post
Not sure how sulfation itself is quantified in order to answer that, without destroying the battery.

I think easier to measure the reduction in SoH% as a result of just that one abuse factor PSOC cycling, all other factors being longevity-optimized.

And would guess yes, AGM loses SoH more quickly as a result.

With the exception of Firefly Oasis of course.

iirc, Lifeline's ability to be equalized did not give any "recovery" advantage over Northstar or Odyssey.

I think best to see that as more of a preventative.
You're reading into this test data what you want to see, since neither of the referenced articles tested a Northstar.
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Old 03-12-2019, 19:38   #8
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Re: AGM batteries, PSOC and sulphation

From my notes, quoting Maine Sail:

Both Northstar and Odyssey are excellent quality AGM batteries and both fended off sulfation better than even Lifeline did, in the PSOC testing, even after the Lifeline was equalized.
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Old 03-12-2019, 20:16   #9
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by john61ct View Post
From my notes, quoting Maine Sail:

Both Northstar and Odyssey are excellent quality AGM batteries and both fended off sulfation better than even Lifeline did, in the PSOC testing, even after the Lifeline was equalized.
I was looking at the two tests referenced in this thread, not your notes or interpretation.
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Old 03-12-2019, 20:20   #10
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Re: AGM batteries, PSOC and sulphation

Based on informal discussions on the docks, I think AGM capacity loss varies for reasons we still don't quite understand - both across brands and even within the same brand. But it does seem to be much worse than either flooded or Gel's.

My last set of Lifelines lasted just over 3 years despite never going below 50%, rarely below 70% and with a concerted effort to recharge them fully within 3 days of a significant discharge. I replaced them with FireFly's

I did not do conditioning because it takes a good bit of a day to monitor the batteries during this 8 hour process and it's impractical unless you are plugged into shore power. Perhaps with monthly conditioning I would have gotten longer life. I'm just not willing to give a day a month to battery maintenance - maintaining a boat is hard enough already.

It's clear to me that whatever is happening to AGM's in normal cruising is worse than what happens to flooded or Gels. Before my several sets of AGM's, I'd had Gels which far outlasted the AGM's.

My casual survey also leads me to believe the situation with AGM's may be getting worse. Lifelines, in particular, seem to have more early failure stories. But this is very unscientific and is - at best - an unfounded rumor. Perhaps I have just happened to talk to an unrepresentative set of Lifeline users.
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Old 03-12-2019, 21:19   #11
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by Paul L View Post
I was looking at the two tests referenced in this thread, not your notes or interpretation.
Easy enough to trace the string back to the post originally discussing his tests if you like.
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Old 03-12-2019, 22:30   #12
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by john61ct View Post
For those not aware, by our own Maine Sail.

Some more details here

https://marinehowto.com/how-fast-can...ery-be-charged

https://forums.sailboatowners.com/th...tteries.171123

Note MS does not state this specific issue, of PSOC causing sulfation, is limited to AGM, it is true for all lead.

Being in general less robust and requiring more precise care, AGM just shows a more obvious immediate impact very clearly in even a short period of time.
I just read your two links from Maine Sail and am not sure they support your last sentence. I don't think I've read that AGM's are any less "robust" than other lead-acid types, and the "precise care" they need is more frequent recharging to 100% (although fxykty's experience suggests YMMV). It's not the batteries themselves but their usage on cruising sailboats without access to shore power that makes them more vulnerable.

I don't know what you mean by AGM's having a "more obvious immediate impact very clearly in a short period of time." Did this come from the PS study in post #1, the MS links, or somewhere else? A "more obvious immediate impact" compared to what? The only non-AGM battery involved in any of the testing that has been cited was a LiFeP04.

Quote:
Originally Posted by john61ct View Post
Not sure how sulfation itself is quantified in order to answer that, without destroying the battery.

I think easier to measure the reduction in SoH% as a result of just that one abuse factor PSOC cycling, all other factors being longevity-optimized.

And would guess yes, AGM loses SoH more quickly as a result.

With the exception of Firefly Oasis of course.

iirc, Lifeline's ability to be equalized did not give any "recovery" advantage over Northstar or Odyssey.

I think best to see that as more of a preventative.
Don't recall seeing Northstar being tested. How do you propose to reliably measure SoH? The Odyssey did retain more capacity than the Lifeline over the 30 test cycles according to PS. Odyssey is not a typical AGM, however, and often disfavored for use as house banks in deep cycle marine applications.

Quote:
Originally Posted by john61ct View Post
From my notes, quoting Maine Sail:

Both Northstar and Odyssey are excellent quality AGM batteries and both fended off sulfation better than even Lifeline did, in the PSOC testing, even after the Lifeline was equalized.
If your notes quoted Maine Sail, then I'm sure you have a reference to where it can be found and can quote it directly. I'd like to read what he wrote and if his interpretation matches up with yours. Has he tested Northstar? Was he measuring capacity loss or actual sulfation? One follows from the other but there are other variables in play.

Quote:
Originally Posted by john61ct View Post
Easy enough to trace the string back to the post originally discussing his tests if you like.
Been there done that. Just the quote from Maine Sail that your notes refer to please.
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Old 03-12-2019, 23:25   #13
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Re: AGM batteries, PSOC and sulphation

Besides avoiding PSOC abuse, for good longevity AGM banks require much more precise voltage regulation as well as stop-charge calibration, ideally based on endAmps.

Regularly holding Absorb overly long can drastically shorten lifespan, since electrolyte lost via venting cannot be replaced.

FLA can be hubble-bubbled for hours no harm done as long as water level is maintained.

The context here is **very often** no shore power available, to which FLA is indeed better suited.

With overnight shore power available, there is no chronic PSOC problem, at least for a competent owner with a charger where both voltage and AHT is user-adjustable.

AGM also require - again for good longevity - a much higher C-rate available than many setups can supply.

FLA thus allows for a much wider variability, even withstanding what would have to be called carelessness with AGM.

Odyssey are very often used for House banks, excellent deep cycling performance, even in their 12V automotive sized models labeled "dual use".

And yes Northstar was tested, both they and Odyssey resisting PSOC damage better than Lifeline despite the equalizing advantage.

Maine Sail spells out his SoH measurement methodologies in the "accurate BM" post.

Again, no idea how sulfation itself could be quantified without cutting the cells open, in all cases losses in SoH as a result of PSOC sulfation is the practical benchmark, and indeed more relevant.
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Old 03-12-2019, 23:27   #14
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by Exile View Post
Just the quote from Maine Sail that your notes refer to please.
Already given

Quote:
Both Northstar and Odyssey are excellent quality AGM batteries and both fended off sulfation better than even Lifeline did, in the PSOC testing, even after the Lifeline was equalized.
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Old 03-12-2019, 23:54   #15
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Re: AGM batteries, PSOC and sulphation

Quote:
Originally Posted by john61ct View Post
Already given
With no attribution. Meaning you're likely misquoting. But you can try again if you'd like. Show us the Northstar test while you're at it though. Or don't -- I think most already get it so have learned not to waste their time.
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