AGM vs Flooded House batteries

[OS2Dude]

We switched to AGM G27s from the G24 FLAs that came with the boat.

Initially it was due to the maintenance issues. Where ours were it was very difficult to check the water level and even harder to top off. After ruining a few pairs of pants with electrolyte spills, I had had enough. The icing on the cake was finding out AGM batteries can be mounted on their sides which let me move them to a much easier location and also one that helped with the boat balance.

I find FLA to be too risky to have aboard, especially if they are not in a place that allows ease of access yet can hold them securely on a heel or a full knock-down.

[rslifkin]

PSOC refers to partial state of charge. Basically, it's what happens for most without solar when away from shore power, where the batteries get drained to say, 50%, then partly recharged to say, 90%, but rarely reach full charge.

[belizesailor]

Originally Posted by tkeithlu

I'm going to stick with flooded, but I'm curious. What is "PSOC" operation.

Thankfully, my system will bring the whole bank to full charge in a few hours. That's one advantage of a power boat.

PSOC = Partial State of Charge. Explained in post above.

IMHO AGMs are better suited to power vessel use, esp if you move around often. Do you spend extended time at anchor? Do you have a generator?

[a64pilot]

Originally Posted by tkeithlu

Thankfully, my system will bring the whole bank to full charge in a few hours. That's one advantage of a power boat.

No matter how large the charge source, it takes about 6 hours to completely charge batteries, the batteries will only accept it at a steadily decreasing rate.
My sail boat has 185 amp worth of chargers not including the Solar, that’s more than most power boats, but it still takes about 6 hours to fully charge
It very much a limitation of lead acid batteries, most live with PSOC and change batteries when they become excessively sulphated. Sort of like tires on a car, when they wear out, you get new ones.

[rslifkin]

AGMs are a little easier to avoid PSOC, given a big enough charging source (large solar, etc.). The high charge acceptance rate lets you get the high amp bulk charging done earlier in the day, leaving more hours for the slow top-off afterwards. It's not a massive time difference for total time to full charge, however. Maybe an hour or 2 faster depending on the setups in question.

Gel batteries handle PSOC a bit better than AGM or flooded.

For the AGMs on powerboats comment, I'm not sure about that unless you're moving a long distance every day. I'm intending to add a big solar setup at some point to avoid PSOC issues. Currently, if I move an hour or so every day I can keep up with power demand without running the generator other than when I actually need it. But I can't avoid PSOC in that usage, as the batteries never get topped off until I'm plugged in at a dock. A good chunk of solar will be enough that even if I don't move, the morning generator run for hot water and breakfast followed by solar during the day will get things pretty well topped off.

[KP44]

Originally Posted by Bill O

Now that you decided to stay w/FLAs, go for the golf cart 6V batteries.


A great bang for the buck and will last longer.


We are on yr. 8 w/ours and will probably go for at least another year before we change them.

I got about 12 years from my first set of 8 Trojan 6 volt.

Replaced with with 3 size D AGMs that never seemed to work as well. Two of them cracked and leaked after a few years.

I took out the AGMs and bought 8 regular golf-cart-type 6 volt flooded. They are doing fine but only 2 years old.

[a64pilot]

AGM’s will accept a higher initial charge rate, so you can get to an initial higher SOC faster with a big charge source, but it still takes about 6 hours give or take to fully charge them. Exceptions are of course very shallow discharge and very good, very new batteries, maybe first couple of months old kind of batteries, as they age it takes longer.

This article explains it much better than I can, be sure to note the difference in time between a large charge source and a small one, it not as much difference as we would expect.
https://marinehowto.com/how-fast-can...ry-be-charged/

The time it takes to charge a battery is why when someone says my batteries are fully charged by noon from Solar, they are almost certainly wrong.
Now if it’s Summer and your way the heck up North where there is 16 or 18 hours of daylight, we’ll then you may well be fully charged by Noon, but for the rest of us that are working with a 12 hour day and don’t get good Solar until almost 10 AM, we don’t have a chance to be fully charged at noon, for us it’s 4 PM if at all.

[sailjumanji]

I had three Deka group 31 AGM batteries in a house bank that lasted for 12 years. The first six years they were charged only via solar power, as we had no shore power setup. Occasionally thye would get overcharged by running outboard engines for long periods. The solar had an MPPT controller. After 12 years, one of the batteries wouldnt hold a charge so we replaced all three. Deka is made by East Penn. I also think the Sams Club Duracells are made by East Penn.

[roverhi]

Originally Posted by OS2Dude

We switched to AGM G27s from the G24 FLAs that came with the boat.

Initially it was due to the maintenance issues. Where ours were it was very difficult to check the water level and even harder to top off. After ruining a few pairs of pants with electrolyte spills, I had had enough. The icing on the cake was finding out AGM batteries can be mounted on their sides which let me move them to a much easier location and also one that helped with the boat balance.

I find FLA to be too risky to have aboard, especially if they are not in a place that allows ease of access yet can hold them securely on a heel or a full knock-down.

Remote watering systems make FLA maintenance a non issue. Just plug the bulb pump into the watering system, put the other end in your jug of distilled water, give the bulb a few pumps till you get back pressure and you're done. Can do from anywhere on the boat and never have to pop the caps on the battery(ies) or even look at them.
This is one system but others out there. https://www.flow-rite.com/battery-ca...ies/qwik-fill/

The cost of AGM's make them an overly expensive source of storage without any benefits for NORMAL use. I can buy 450 amp/hours of GC battery storage for $400. AGM's can be 3 times that and may not be any more long lived in the real world of a cruising boat.

[OS2Dude]

Originally Posted by roverhi

Remote watering systems make FLA maintenance a non issue.

I saw an ad for one many years ago about the time I switched. To me, was something else to potentially leak and/or fail with no way to know until the batteries are dead or I'm trying to clean up a battery acid spill. (Perhaps are better now, IDK)

I am 100% Solar (with OEM alternator) ever since my shore charger failed TWICE with no indication of a problem. Well known manufacturer admitted it as a design error and sent me a new one after the first time. (Both AGMs were DOA because of that.) New one also failed for the same reason, but I caught it before the new batteries suffered the same fate. I declined their offer of a third when they said 'they did not know when the fix was implemented' and that another new one could still have the issue. [Sorry, but the company DOESN'T KNOW when they implemented the fix? Not by date or serial number? ] I used the refund to buy the seed of my solar setup.

[Dehler 25]

I currently have six flooded Crown 6v golf cart batts in series parallel with primary recharge from 720 watts of newly replaced solar. My down side is that I have them as a single house bank and not split in two. It would have required the banks not to be balanced and while some may point out that on "both" it should not matter I would be on "both" at all times anyway. I wanted to go to eight batts but space was exhausted. I would like to have the two banks so that if a battery failed I could isolate the bad bank but wonder if a rewire is worth it. I noticed after going from 210 tired watts of solar to the 720 I am charging a lot hotter at 14.5 which causes me to watch the flood level a lot closer as bubble bubble boil to trouble! Opinions?

[Bill O]

Originally Posted by roverhi

Remote watering systems make FLA maintenance a non issue. Just plug the bulb pump into the watering system, put the other end in your jug of distilled water, give the bulb a few pumps till you get back pressure and you're done. Can do from anywhere on the boat and never have to pop the caps on the battery(ies) or even look at them.
This is one system but others out there. https://www.flow-rite.com/battery-ca...ies/qwik-fill/

Looked into a watering system for our 8 Crown golf cart batteries and was quick to find that one needs to find a set up specific to your make/type of battery. The flow rite watering system linked above works for group size 24 through 27 and most 29 through 31, 12-volt marine deep cycle batteries. Hate to spend that kind of money on a system to then find out it will not fit.

Did find this one recently that would work on Crown gc batteries. Even though it is a pain to water the batteries every month, did devise an easier way to do it. The watering "guns" used for fork lift batteries looked promising, but were very expensive. Found that if I took the spray tip off of a 1 gallon weed sprayer it did the same thing and worked well for filling our batteries (always wear safety glasses). The biggest pain is taking the caps on/off, but still prefer seeing if there is any issue w/individual cells which you don't get to observe if one has the other kind of "closed" watering systems.

[Pete7]

Originally Posted by Dehler 25

I noticed after going from 210 tired watts of solar to the 720 I am charging a lot hotter at 14.5 which causes me to watch the flood level a lot closer as bubble bubble boil to trouble! Opinions?

I found this part of your post confusing. Why are the solar panels tired? and what do they now produce in volts and amps?

Do you really mean "hotter" or a higher voltage? hotter implies a temperature rise?

FLA batteries do loose water when used, but then they have caps so you can top them up.

[robert sailor]

Originally Posted by KP44

I got about 12 years from my first set of 8 Trojan 6 volt.

Replaced with with 3 size D AGMs that never seemed to work as well. Two of them cracked and leaked after a few years.

I took out the AGMs and bought 8 regular golf-cart-type 6 volt flooded. They are doing fine but only 2 years old.

If you got 12 years out of golf cart batteries your operating at levels far beyond my abilities...hats off to you

[Dehler 25]

Solar panels like sailors get old and they produce less efficiently, I had them in service for about ten years and they were collectively rated at 210 W 70 per panel, I think before pulling them they were indicating about 40W total on a good day and guessing that they never pushed over 13.5V. The new panels on an MPPT indicate 14.5 charging and without watching often have seen them over 500W and would blow a fuse less than thirty amps. The higher charge voltage does make bubbling in the batteries common so the lose water faster than they did. I just topped them up Sunday and it took an entire gallon to refill all six. Adjusting to too much power is not a bad thing.