AGM as house Bank

[Dockhead]

We used AGM 4D's on the previous boat. They lasted longer after we installed a large solar array which was usually able to top them off most days.


The AGM's had very poor cost per cycle, or cost per year. They are 2x or 3x more expensive than golf cart batteries and last 1/3 or maybe 1/2 as long if you are off grid much. We had not choice on that boat because the batteries could not be installed where they could be watered, and that was before lithium.



Lithium causes some brain damage and some cost doing a proper installation but surely is cheaper and better in the long run.


If not lithium, then 6V golf cart batteries. They are cheap and more robust and more tolerant of the kind of usage we put them through. Only way to go provided you can get to them to water them.

[Icarus]

Originally Posted by Jamme

In my view, it all depends on intended use and recharging capabilities. I am a mostly weekend sailor, and because I have no solar or genset, my AGMs were done in a couple of seasons — the issue being that I was out for a couple of 2-week trips and AGMs did not appreciate the extended partial charge I gave them from my standard alternator.

So, back to old flood for me. As said, your experience may vary.

Fair winds.

Looking at the drama to keep AGMs fully charged and their cost I am happy with Trojan125 T
Four 6Volt batteries cost me 1200 AUD and the last set lasted 7 years...about 45cents a day....

[MVDarlin]

I used 6xOptima AGMs for house. Most failed premature. They were routinely left uncharged in high heat each summer. Expensive batteries.

[wrwakefield]

Originally Posted by Dockhead

...
If not lithium, then 6V golf cart batteries. They are cheap and more robust and more tolerant of the kind of usage we put them through. Only way to go provided you can get to them to water them.

Just an FYI re: centralized watering systems for FLA batteries.

In 2014 we replaced our house bank with Trojan T105s (Full time cruising; still going strong...)

Our bank is inaccessible, so I installed a Trojan Hydrolink centralized battery watering system.

FlowRite (and likely others...) also makes battery watering systems for about any brand FLA battery.

This makes FLAs very appealing when it takes less than a minute to water the entire bank without having to access individual batteries (8 batts in ours)- and it can be set up for gravity flow when away from the boat for extended periods...

Perhaps not on track with the OP's question, but FYI for anyone interested.

Cheers, Bill

PS: (Too many...) Details about our house bank upgrade are in this blog post- complete with photos of our ugly installation and links to external resources.

[chrisr]

i'm a little surprised at the discussion regarding adding water to batteries

i haven't seen this sort of battery for years (in any application...cars / boats / etc)...they are all sealed these days i thought

can somebody tell me what is the benefit to this sort of battery, that outweighs the disadvantage ?

cheers,

[Davidasailor]

Our boat came with a 2x G31 AGM (Deka Intimidator) house bank in 2014, 80A standard alternator and 20A shore charger. We’re your typical weekend sailor doing lots of day sailing and a handful of overnights per season. After 7 seasons I did a 20 hour load test and found both batteries still over 100AH. Half way through their 9th season, last summer, they both gave up. One got a bad cell and would quickly fall to 11V at rest, and the other tested at 75% capacity. We replaced with exactly the same model with no apprehension. This winter we’re adding a third equivalent battery to the bank to extend the time available before recharging a little.

It’s nice not needing to worry about watering them at all. The slow wintertime self-discharge is great. We disconnect everything in November. I stop by once in January and top them off while I do some chores, but they’re still at about 99.5% SOC so that’s probably unnecessary.

[Dockhead]

Originally Posted by chrisr

i'm a little surprised at the discussion regarding adding water to batteries

i haven't seen this sort of battery for years (in any application...cars / boats / etc)...they are all sealed these days i thought

can somebody tell me what is the benefit to this sort of battery, that outweighs the disadvantage ?

cheers,

Sure. Flooded lead-acid batteries designed for bulk power storage (a very different use case from starting batteries) are cheaper and more robust in that type of service than AGM or gel batteries. Downside is you have to water them.

[GILow]

Originally Posted by chrisr

i'm a little surprised at the discussion regarding adding water to batteries

i haven't seen this sort of battery for years (in any application...cars / boats / etc)...they are all sealed these days i thought

can somebody tell me what is the benefit to this sort of battery, that outweighs the disadvantage ?

cheers,

The Trojan T105 needs watering. I suppose it depends on where they are installed, but on my Swanson access is very good and they are a simple job, once every month I check, once every six months I add a little water. The six batteries have used less than five litres of distilled water in four years between them.

The benefit? Well, I don’t know of many people who were unhappy they installed the T105s. They just seem to work, and work, and work. I’d put them in the new boat but I’m going all electric with the galley and I was going to need 300 kg of batteries unless I went lithium. I decided, reluctantly, to go lithium.

[Davidasailor]

Originally Posted by chrisr

i'm a little surprised at the discussion regarding adding water to batteries

i haven't seen this sort of battery for years (in any application...cars / boats / etc)...they are all sealed these days i thought

can somebody tell me what is the benefit to this sort of battery, that outweighs the disadvantage ?

cheers,

There is a difference between sealed flooded lead acid batteries, often marketed as “maintenance-free”, and sealed Gel or AGM lead acid. “Maintenance free” flooded lead acid are ok for places like cars where they don’t get deeply discharged and go through long hot recharge cycles, but are poor choices for deep cycle use. The problem is that when recharging the maintenance free batteries can still boil off some electrolyte, and there’s no way to replace what’s lost. Eventually the electrolyte will be lost to the point where the plates aren’t fully covered and capacity begins to suffer.

[sailorboy1]

Used to be a great fan of the FLA golf cart batteries. They were just such a great value compared to AGMs and took a lot of abuse. I had 2 sets in 8 years and for the $15-20/month cost use thought they were great.

But at $250/ea they just don't really hold up value wise anymore when you can get LFP 100ah drop in batteries for $300. And of course the LFP for a house boat battery just has so many other pluses and it is an easy install once you stop listening to the "let's make this very complex" people".

Which brings back the original thread post of AGM batteries. These seem insane compared to the LFP option.

[Dockhead]

Originally Posted by sailorboy1

Used to be a great fan of the FLA golf cart batteries. They were just such a great value compared to AGMs and took a lot of abuse. I had 2 sets in 8 years and for the $15-20/month cost use thought they were great.

But at $250/ea they just don't really hold up value wise anymore when you can get LFP 100ah drop in batteries for $300. And of course the LFP for a house boat battery just has so many other pluses and it is an easy install once you stop listening to the "let's make this very complex" people".

Which brings back the original thread post of AGM batteries. These seem insane compared to the LFP option.

I don't know about drop-in lithiums, but a properly done LiFePo4 system is certainly better in every way than any lead battery system - much better in operation, lighter, cheaper per cycle.

Golf cart batts are the best only among other lead batteries.

I agree with you that AGM seems crazy for our use case.

[sailingharry]

Originally Posted by GILow

The Trojan T105 needs watering. I suppose it depends on where they are installed, but on my Swanson access is very good and they are a simple job, once every month I check, once every six months I add a little water. The six batteries have used less than five litres of distilled water in four years between them.

And you can cut that use down even farther by using specialized replacement battery caps that collect off-gassing moisture and allow it to drip back in. I had Trojans, and then Sam's Club golf cart batteries on my last boat, and adding water was an exceptionally rare situation.

My current boat came with AGM, and I do like the maintenance free side of it, but I have been very frustrated with the charging regimen. They will be replaced with lithium when that time comes, but if LFP didn't exist, they would be FLA batteries for sure!

[sailorboy1]

Back in my T105 days the batteries only needed watering every 2 months. Doing it wasn't a big issue in my time.

The only thing about the "drop in" LFPs are that people have been reading for years how complex installing LFP is. Now they can not believe that maybe this is wrong.

If you install drop in LFP at $600/200ah compared instead $500/220ah T105s and they "only" last the same amount of time as the T105s would, you should be happy. If you want to spend $4000-$6000 instead to get "the best" LFP and spend another $1000+ for stuff to monitor and care for them so they made it 10+ years go ahead as boaters love to make things complex.

My 4x100ah drop in LFPs cost me $1319 including shipping. Installation costs were about $10 for longer bolts for the terminals. The same Battleborn drop in would cost $3496.

I am pretty sure we know how this goes. Boaters believe in the mystery battery box more if it has a bigger price tag.

BTW - I have no ideal if my Power Queen $306 batteries are going to last. In fact I only expect them to last 4-5 years. My last set of T105s lasted 3 years before a solar problem when I was away for a week drained the batteries. My $2000 set of FireFly batteries lasted 2.5 years before showing they were not any better than AGMs. Who can really say what the LFPs are going to do.

[AKA-None]

Originally Posted by chrisr

i'm a little surprised at the discussion regarding adding water to batteries

i haven't seen this sort of battery for years (in any application...cars / boats / etc)...they are all sealed these days i thought

can somebody tell me what is the benefit to this sort of battery, that outweighs the disadvantage ?

cheers,

They are pretty much dirt cheap to buy

[Simi 60]

Originally Posted by AKA-None

They are pretty much dirt cheap to buy

Depends where you are

In Australia it was cheaper for me to build a lifepo4 bank with double the capacity of a T105 bank
Same with AGM, got double lifepo4 for less $$