AGM for House Batts?

[FF]

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 .

 

[DavidM]

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.


David

 

[timjet]

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.

 

[CMS]

Which Practical Sailor article or issue/issues are you referring to?

 

[rwidman]

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.

 

[Nomad Willy]

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?

 

[CMS]

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.

 

[DavidM]

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.


David

 

[AKDoug]

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.

 

[Nomad Willy]

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.

 

[psneeld]

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.

 

[CMS]

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.

 

[HenryD]

Unfortunately you need to be a subscriber to read the articles.

Fighting Sulfation in AGM Batteries May 2015

AGM Battery test Update August 2015

 

[Rain Dog]

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

 

[AKDoug]

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.

 

[MurrayM]

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?

 

[AKDoug]

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.

 

[HopCar]

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.

 

[markpierce]

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.

 

[dhays]

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.

 

[N4712]

We have 9 8D's and one 4D, all AGM. The access from above isn't too conducive to checking potential water levels and also I like not having to monitor them. We have Lifelines and love them. Going on 3 years, all is good. (we replaced them when we bought the boat). Albeit not cheap but I think it's made up in for the lack maintenance needed.

 

[AusCan]

I've moved my battery boxes to an area with limited ventilation so Lead Acid batteries aren't a good option.

I've had early failures with low priced AGM starting batteries, (<2 years) but the same brand of deep cycle house batteries seem much more forgiving. I plan to switch to an AGM deep cycle for my start battery as well.

 

[FF]

"So what the hell is standard crusing practice? and how is the "standard cruiser" using and charging batteries"

"Std cruising" for folks that prefer to anchor out and not run from power pole to power pole is to almost NEVER have the house bank back to 100% full. 85% SOC down to 50% seems the norm , with an over sized batt bank to allow for the sloe capacity loss from undercharging LA batts.

The time it takes , many hours for the last 5-15% is way beyond what most folks will operate a noisemaker for.

And a 8 hour main engine run might not be long enough for 100% either.

The only folks that have a chance of a proper recharge have well installed solar

or a wind generator for the anchorage to listen to 24/7

Rain Dog post 14 seems to have it right.

No full 100% recharge , tiny service life.

 

[psneeld]

FF...I know you have been out there and talk to a lot of people....but is that your definition or PS's definition of average cruisers....and is it really that accurate any more?

But since the advent of solar, better charging/monitoring set ups, better batteries, a larger percentage of power boats as long term cruisers, more sailing cruisers with gensets...etc.... I have a hard time saying there is an "average" anymore....I see cruisers all the way up and down the "guy with a multimeter in hand all day" to the clueless "hey...I just bought my first boat and am leaving for the islands tomorrow".

 

[SCOTTEDAVIS]

Like many of you I have a large house bank comprised of golf cart LA batteries in a somewhat remote location and in boxes. I have found an ideal solution to keeping them watered easily and quickly and without bending over.

I offer...

https://flow-rite.com/pro-fill-bom/

 

[RCook]

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.

Indeed - something like that seems to be the explanation for bad results with AGM's on the sailing-oriented Cruiser Forum. Also a lot of sailors seem to spend time hanging on a mooring or at anchor without a charging source.

I explained on Cruiser Forum how well AGM's have worked for me (11 years - summer cruises, mostly anchoring out - from a pair of g31 Deka AGM's), and the reaction was skeptical. When I provided details, backed up with Link 2000 data, there was some acceptance.

In my case, with a small house bank, and excellent and properly-sized Balmar charging system, running 6 hours or more most days, I think my AGM's get pretty well recharged pretty often.

In addition to being maintenance-free, and not leaking/corroding, they sit out in the cold all winter with little self-discharge, and no worry about freezing damage.

I like the tradeoffs.

 

[FF]

"I have a hard time saying there is an "average" anymore.."

Next time you visit a boat cruising and see 100% on its SOC meter (if its not at the power pole) , you have visited a non "average" boat.

By My Daffynition.

The above post with 6 hours of running Every Day would qualify.

The only time we see 6-10 hours a day is in transit , never when cruising locally.

Life will get lots better as the current crop of coal powered cars have their battery packs removed and rebuilt.

The various Lithium batts should do great at our needs , if they don't catch on fire and the very complex charging is done properly.

The various roll your own electric car sites explain the battery rebuild process.

 

[folivier]

Since you brought up "lithium batteries".... Lithium Iron Phosphate is the way to go. And the charging is actually very simple: just pump as many amps as you possibly can into them and don't worry if it ever reaches 100% or not. There is no acceptance charge or any need to equalize. As long as it is a properly installed system with LV & HV cutoffs.
Too bad LiFePO's are not being produced quickly since they are really a great system.

 

[drb1025]

I have Lifeline AGMs for my inverter bank. The manual says that "conditioning" (aka equalizing) should only be done when the battery is showing symptoms of capacity loss due to extended time in a partial or low state of charge condition. I have not conditioned them yet and have not noticed any capacity loss. When the manual states that it "should only be done" when showing symptoms, it sounds like it is a harmful process.

 

[Bacchus]

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.

I'm in the "same boat" w/ boat under cover for 8 mos and no way to keep charged. I have 3 8D's start / house + Gp 28 gen start batt'y and the yard was not cooperative when asked to remove my FLA 8D's to keep them on a charger over winter.
I loved mt previous boat & 6V Gold Cart FLA house batt'ys but have chosen to go the AGM route - for now vs rewire to accomodate different batt'ys.
East Penn / Deka 8D AGM's were still at 12.8V after winter storage their first year - will continue to monitor.

Lots of different reasons for our choices and I'll reconsider after I need replacements but for now they are doing exactly what I hoped they would and I couldn't be happier.