Gel or Flooded?

[a64pilot]

Here is the issue, Gel is almost certainly “better” no maintenance and almost certainly lasts longer.
Due to sizing constraints, I’m pretty much stuck with a group 31 battery, and in that size you can get a good quality flooded battery for $1 an AH.
Gel costs roughly three times as much.
So for a 600AH bank it’s $600 for flooded and $1800 or more for Gel.
I say more as I’ve not really researched shipping costs etc, the flooded I can pick up myself at Sam’s club so I know it’s $1 an AH, less tax.

So is Gel worth three times or more cost? Will a group 31 Duracell (Deka) flooded battery last five years in actual use?

I want Gel, but am having a hard time convincing myself it’s worth the additional cost

[rslifkin]

To me, the price premium of gel or AGM is worthwhile for the reduced mounting constraints, not having to deal with top offs and most importantly, reduced risk of acid drips, venting, etc. around the batteries.

I've generally seen gels last longer than most of the other 12v deep cycles (flooded or AGM). But probably not 3 times as long, so flooded is still most likely cheapest.

[a64pilot]

So how often do you need to add water? I have AGM now and of course don’t, but I figure it’s a once a month task, I know how often will depend but still am under the impression that it’s once a month.
It’s value I’m trying to determine, Firefly for instance is I believe over $5 an AH, and to me that puts them way overpriced.

[NewMoon]

Gel certainly lasts much longer than most others. I replaced original 4D Deka gels in my 2002 Nordic Tug in 2016, after cruising 800 hours with them that summer.

I presume you know they will require different charging voltage settings for longest life.

[ranger58sb]

We have both Odyssey and Lifeline AGMs. At least our first set of Odysseys lasted about 12 years, but the verdict is still out on the other bank of Odysseys (10 years and counting) and the Lifeline bank (3 years and counting) that replaced the first Odysseys.

Much more expensive than FLAs. Longevity aside, almost all the benefits I was after are about mounting- and service-related issues, i.e., not having to yutz with them. I could get more of the Lifeline 4CTs in there, wouldn't even have been able to do that with FLAs 'cause service would become a nightmare. Priceless. To me.

But if service were easy... seems hard to beat $1/Ah, with minimal cash investment periodically.

-Chris

[ronstory]

A64--

The Group31 size makes it hard, that's the challenge I have as well. I would love to put in 6V FLA golf cart batteries with "auto" waterers, but they are just too tall.

In my case, I'm going LiFePO4 with a FLA/AGM starting battery, but I'm a geek. If I wasn't a looking forward to building my own BMS system, I would look hard at Firefly since they fit a G31 form factor. And MaineSail says good things about them.

[GordMay]

Originally Posted by NewMoon

Gel certainly lasts much longer than most others. I replaced original 4D Deka gels in my 2002 Nordic Tug in 2016, after cruising 800 hours* with them that summer.
I presume you know they will require different charging voltage settings for longest life.

Indeed.
* Battery life should be measured in discharge cycles, not by time.

Lithium is the premium option, with a higher efficiency, longer lifespan, and fewer maintenance requirements, than any of the lead-acid batteries.
Flooded lead-acid batteries are the most cost-effective option, and longest lasting of the lead-acid batteries, but require (monthly) upkeep; whereas sealed lead-acid batteries (AGM & Gel) cost, more but do not require regular maintenance
AGM batteries resist vibration, and can handle higher charge/discharge rates (than Gel), but gel batteries can withstand higher temperatures, and last longer. For example, discharging a gel battery at 30% gives you about 2,600 cycles, compared with only 1,200 cycles with AGM batteries.
AGM Batteries outsell Gel Cells by at least a 100 to 1.

[a64pilot]

Lithium is still in my opinion a science experiment.
I’d be more likely to go that way, if I wasn’t spending most of our cruising time where even a light bulb just isn’t available.
I desire old proven tech.
Charge voltages etc are no problem for me, everything is programmable and I could even go Lithium if I desired. I know the advantages, I see the attraction, and would be more likely to do so if there were a complete kit that I could buy.
I could have built my own watermaker, but bought a Cruise RO because it was a complete kit, with everything already there.
Some reputable source needs to build a LFP kit

Firefly at over $5 an AH is insane to me, that over $3,000 for a 600AH bank.

I may go Gel, but the cost savings of flooded is very attractive.
It will be late Summer before I do anything, we are out cruising now.

I saw a significant loss in capacity of my bank this year, that I can’t explain and isn’t recoverable by equalizing, but makes me think that possibly my bank is nearing its end of life and I don’t want a failure out where no batteries at any cost are available.

On edit, part of what’s driving is that it’s very unlikely I will need a bank that lasts ten years, anymore than if I bought a house that I would need a 30yr roof.
I don’t expect to be on the boat more than six more years, and if I get that I’ll consider myself lucky.

[ronstory]

Depends on your energy usage and whether you can keep them fully charged in your typical cruising activities. Gel and AGM, just like FLA, like to be 'topped off'. Solar is great for that, since the absorption time for those LA acid variety can be long. FF are more forgiving to PSoC and Lifepo4 doesn't really care unless you completely drain them.

FF are more forgiving to deeper discharges for more available so you may not need a 600AH pack to get the same effective usage.

If you can keep them topped off, Gel or AGM are fine.

[a64pilot]

I can keep them full, I do so now with my AGM bank, Although at times it’s a pain.
I thought that Gel was more tolerant for PSOC?
I’ve heard the advertising on Firefly, and while it may be true, I don’t completely buy into it, certainly not enough to undersize a bank and discharge it deeper anyway.
Lithium, sure, but there I would I believe want to cycle between 40% and 80% SOC, based solely on that’s how at least one major hybrid car manufacturer does it.

Not meaning to get this into a lithium thread, just saying that as I use about 150 AH nightly, I would want a 400AH lithium bank.
I’d like to have an 800 AH lead bank, just can’t fit it without losing another storage bin, and I don’t want it that bad.
But a 600 AH bank I’ll discharge 25% at night cycling it between 75% and 100%. Assuming it really is a 600AH bank, I don’t know what it really will be compared to it’s rating?

However 25% discharge should give me plenty of reserve and still give a long life?

I was never really an AGM fan, I love them for my auto’s and airplane, but not for my house bank in a cruising bank.

[rslifkin]

My understanding is that Gel is somewhat more tolerant of PSOC than AGM or Flooded (AGM being the least tolerant of it). But it's still not super tolerant of it.

How much vertical clearance do you have over the spot for your group 31s? Or is there another spot you could move the bank to that's of similar footprint but taller?

[a64pilot]

9.75” is really pushing it, it’s actually about .25” too tall.
Yes I could put batteries in a storage area, but if I do that, and it’s a thought, then I’d go to the super big Flooded Trojan Solar batteries, probably the SPRE 12 25.
I don’t understand why they are not used in boats more often.
Look at the expected life cycle chart

http://www.trojanbattery.com/product...ine-flooded-2/

Seems $2 an AH, but look at the cycle life

However it’s just easier to put the batteries where they were intended. In truth I do have to put some batteries in a storage space as it is, the factory battery box just isn’t big enough.

According to my original 1987 owners manual, the boat came with the then very new Sonnenschein Prevalier batteries, which according to the manual was a German battery designed for military use, specifically NATO, in what use, I don’t know.

Near as I can tell the Sonnenschein Gel battery in the US is the prervebial unicorn, there are rumors, but no source that I can find

[rslifkin]

In the US, I'm pretty sure the East Penn made gel batteries use the same tech as Sonnenschein, as they licensed the tech years ago. And East Penn makes pretty good batteries in general.

[s/v Jedi]

Are all the batteries for house bank or also for starting? If you have a separate starting battery which needs to be backup for house as well, then the very best fit is the Odyssey thin plate pure lead which is available in group 31.

If it is purely a house bank then I would opt for the Lifeline AGM over gel or Firefly. My reasoning: gel is best for Sonnenschein 2V cells of 900Ah and up and Firefly is halfway up a Battleborn LiFePO4 which makes that a better buy but again more money.

I went with the Odyssey start battery and a bank of 4x Lifeline L16 house bank, leaving room for further experiments once I have upgraded my solar array

[rslifkin]

I guess I should mention what I settled on for my setup. Currently my 2 start batteries are West Marine brand (made by East Penn) AGMs (group 27). House bank is 2x Mastervolt L16 AGM.