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Old 03-15-2016, 07:48 AM   #1
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AGM for House Batts?

Folks that cant wait to pay double for AGM as house batts might want to invest in a subscription to Practical Sailor .

AGM seem to do worse at std cruising practice (almost never seeing 100% recharge) than good old golf carts .
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Old 03-15-2016, 08:52 AM   #2
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While Practical Sailor may be right, I wonder how they came to that conclusion. Did they set up a controlled test of several types of batteries, discharging them and (mostly) recharging them over hundreds of cycles? That would be PS' normal test method. Or did they interview cruisers, which is very subjective.


But I suspect that any long term cruiser with solar panels (and most cruisers should have them), do get their batteries fully charged at least once or twice a week, so partial recharging should become less of an issue.


Not that I am defending AGMs. In almost all cases I prefer golf cart batteries for house use.


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Old 03-15-2016, 09:24 AM   #3
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AGM's on my boat are a necessity. They are set up in 3 layers, so to view or add water to the bottom layer would require removing the upper 2 layer of batts. Ain't gonna happen.

Accessibility or the lack of is one reason AGM's are used in some boats and RV's.
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Old 03-15-2016, 09:30 AM   #4
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Which Practical Sailor article or issue/issues are you referring to?
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Old 03-15-2016, 10:36 AM   #5
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Quote:
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Folks that cant wait to pay double for AGM as house batts might want to invest in a subscription to Practical Sailor .

AGM seem to do worse at std cruising practice (almost never seeing 100% recharge) than good old golf carts .
Posting that without a link helps nobody. And a magazine subscription can't start a boat engine.

Some of us have AGMs for reasons other than cost.
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Old 03-15-2016, 10:51 AM   #6
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The advantage to AGM's is that it takes less batt to do the job.

Lead acid (LA) batts can only discharge (useable) down to 50% of full charge. AGM's can routinely be discharged 80% whereas LA batts only 50%. If we (we have AGM) were to switch to LA we would need 1/3 more space for our house batts. No space in the engine compartment for that. We'd need to buy a new start batt too as the charging rate would not be high enough for the start batt if we changed the house to LA.

New batts may be very soon in my future and I'd love to spend lots less. Our battery power is rather minimal now so LA batts may mean we could only run the Wabasto part of the night. And if money were no issue what case could be made for not using AGM's?
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Old 03-15-2016, 11:08 AM   #7
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The advantage to AGM's is that it takes less batt to do the job.

Lead acid (LA) batts can only discharge (useable) down to 50% of full charge. AGM's can routinely be discharged 80% whereas LA batts only 50%. If we (we have AGM) were to switch to LA we would need 1/3 more space for our house batts. No space in the engine compartment for that. We'd need to buy a new start batt too as the charging rate would not be high enough for the start batt if we changed the house to LA.

New batts may be very soon in my future and I'd love to spend lots less. Our battery power is rather minimal now so LA batts may mean we could only run the Wabasto part of the night. And if money were no issue what case could be made for not using AGM's?
Every AGM manufacturer I know of, except for Firefly, advises a maximum cycling depth of 50%.

You can just as easily cycle deep cycle flooded batteries to 80% DOD but the cycle life suffers, just as it does with AGM's...

Some manufacturers, such as EnerSys, still advertise 80% DOD but then recommend a max DOD of 50% because the cycle life at 80% DOD really suffers quite badly.
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Old 03-15-2016, 11:10 AM   #8
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Eric:


I have read conflicting advice about discharging AGMs beyond 50%. Do you have a reference for your claim that AGMs can be safely discharged beyond 50%? On a related point, some say that AGMs don't sulfate when left discharged. Some say that they sulfate just like FLAs.


Besides cost, the main advantage to flooded cell golf cart batteries is that you can check their specific gravity to know their real state of charge.


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Old 03-15-2016, 11:52 AM   #9
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I am a PS subscriber, and I bought AGM's for my boat after researching their articles on house batteries. I am curious what context that quote was taken from too...

I have access issues with the tops of my batteries and a lack of space for the batteries, golf carts wouldn't work in my install and the AGM's have been flawless so far. I doubt I have discharged below 70% of capacity (30% draw down) and they charge right back promptly with my 100 amp alternator. I never have access to shore power so it's recharge off the alternator or fire up a generator, which never happens either.
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Old 03-15-2016, 01:56 PM   #10
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Got the "80%" from Pacificpower Batteries where I bought my first AGM's .. Life Line brand. They went so early so I bought "Full River" batts as a replacement ... from Boat Electric in Seattle. They said I needed to keep them on the charger all the time .. I had been turning the Xantrex of at times thinking the batts needed occasional exercise.

In a few days I'm going to spend the night on the boat using the heater and lights as we would while cruising. The Full Rivers are about 5 years old. I'll see how they do. The voltage readings on the Xantrex should tell all.
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Old 03-15-2016, 02:02 PM   #11
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Holy cow guys....

FF posted what PS wrote (who I rank up there somewhere's lower than consumer reports and higher than a lot of publications)....

"AGM seem to do worse at std cruising practice (almost never seeing 100% recharge) than good old golf carts . "

"std cruising practice"...what the heck is that? many real cruisers here can't even get it together enough to agree on words like trawler...

So what the hell is standard crusing practice? and how is the "standard cruiser" using and charging batteries...another topic many experienced cruisers here can't come close on....

When are you guys gonna learn? There is so much BS out there in boating rags/books/blogs..only bested here by a few dock queens owners and/or unmechanically inclined that love to quote boating rags and pseudo experts (FF excluded...he does know a lot of stuff)....or like me a life member of the bad boys club just stirring up shi*.

I don't know which type of battery is better for my boat let alone any of yours. Just like our boats...some batteries have features that may suit your needs better...but to say they are better for all cruisers is wayyyyyy out of line....until Practical sailor can make enough of our boats and boating habits alike to form a consensus....it is a WAG.

I got rid of PS and Consumer reports long ago when I saw their limited way they tested things.
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Old 03-15-2016, 02:35 PM   #12
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Practical Sailors most recent look at AGM batteries occurred in the May 2015 and August 2015 issues where the effects of partial state of charge use was examined..

Fighting Sulfation in AGM Batteries May 2015

AGM Battery test Update August 2015

PS does occasionally rehash old articles, sometimes many years old, and send them out as e-book emails.
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Old 03-15-2016, 05:43 PM   #13
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Unfortunately you need to be a subscriber to read the articles.

Fighting Sulfation in AGM Batteries May 2015

AGM Battery test Update August 2015
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Old 03-15-2016, 07:11 PM   #14
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For sure AGMs will be a terrible money sink for some people, and a boon for others. Like most things boat related there is no one correct answer for everyone. For sure one should do their homework before they invest and understand the distinct advantages and disadvantages.

AGMs can take a higher charge rate, but most boats do not have the capacity to charge that fast anyway. Many people report terrible AGM cycle life if they are not fully charged regularly. For example Lifeline Battery Company claims AGMs will last:

- Fully charge after each discharge. Estimated life: 6-9 Years
- Fully Recharge at least once a week and equalize once a month. Estimated life: 4-6 Years..
- Only recharge to 85% and equalize once a month. Estimated life: 2-4 years.
- Only charge to 85% and never equalize. Estimated life: 1 year.

Lots of great info here: AGM Batteries - Making The Choice | SailboatOwners.com Forums
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Old 03-15-2016, 07:17 PM   #15
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Someday I will let you all know when I replace my Lifeline AGM's. So far I have two years on a pair of 4D batteries and a group 31 start battery, which I run hard all summer and never charge in any way except by running the boat.

They sit for 8 months during the winter with no charger on them and have plenty of life in the spring to fire it up and go into "float" mode within an hour. I anticipate 8-10 years of service life, but we will see... I have an amp hour meter plugged into a hole but not wired, hopefully before launch this season.

PS is worth the price (to me), although admittedly I don't get something out of every issue that is useful to me.
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Old 03-15-2016, 07:24 PM   #16
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Someday I will let you all know when I replace my Lifeline AGM's. So far I have two years on a pair of 4D batteries and a group 31 start battery, which I run hard all summer and never charge in any way except by running the boat.

They sit for 8 months during the winter with no charger on them and have plenty of life in the spring to fire it up and go into "float" mode within an hour. I anticipate 8-10 years of service life, but we will see...
Nobody can accuse you of coddling your batteries!

If you recall, what was your last setup and how long did they last?
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Old 03-15-2016, 09:19 PM   #17
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The last setup was what the boat came with, 3 group 26 batteries with one start and the other two house on a 1/2/both switch. If I cruised every day I could keep them up, if I sat for a day the refrigerator started making funny noises... I ran my generator a lot if I sat on the hook, but that summer I had an A/C range, no heat, and the summer was cold so I ran the Honda a lot.

I am sure the seller put them in just for the survey. The space is very limited for my batteries so I have exactly as much batteries as will fit in that space.
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Old 03-15-2016, 09:40 PM   #18
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It's Practical SAILOR magazine. Their typical practice is to only charge their batteries to 80 percent because they hate running engines or generators. That last 20 percent takes a long time to get. If you run your engine or generators to bring the batteries up to 100 percent fairly often, I think your results might be different than PS magazine found.

I use AGM batteries because I can lay them on their sides. By doing that I was able to put them in a space they wouldn't fit standing upright. This freed up a lot of floor space around my engine.
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Old 03-15-2016, 09:50 PM   #19
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My boat came with AGM batteries. No complaints yet after five years. The house batteries are on the port side of the engine compartment and the engine-starting batteries are on the starboard side. The boxes make for convenient seats while working in the compartment.

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Old 03-15-2016, 10:01 PM   #20
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It's Practical SAILOR magazine. Their typical practice is to only charge their batteries to 80 percent because they hate running engines or generators. That last 20 percent takes a long time to get. If you run your engine or generators to bring the batteries up to 100 percent fairly often, I think your results might be different than PS magazine found.
Many sailboats came with terrible alternators as well (like my 80amp Hitachi) that has a really hard time fully charging a battery even when I motor to my next destination.
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