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Old 04-12-2012, 01:27   #16
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Re: Need new Gel Batteries in Florida

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Originally Posted by Maine Sail View Post
You will get more cycles out of GEL than with AGM...
I think this too much of a generalization - any statistics to back it up?

Many people don't make the best of their AGMs with proper charging regimes, which is maybe why you make your claim.

Not all AGMs are the same - and I'm not sure that the Deka mentioned above is the most suitable true deep cycle for a cruising sailboat. Too much of a dual purpose high CCA battery. I think the Gel/AGM cycle chart above comes from Lifeline, who used to make Gel batteries. They finally decided AGMs were so much better in every respect that they abandoned Gels, which is an old technology from 1956.

I'm been a full time liveaboard in the Med for 7 years and my Lifeline AGMs are now 8 years old. Anchor most of the time except in the winter months.
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Old 04-12-2012, 09:40   #17
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Re: Need new Gel Batteries in Florida

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I don't agree.

Problem with that graph, as with all "sales tools", is just what is the "leading GEL battery"?????

I tend to prefer to focus on companies who sell GEL, AGM and Flooded batteries such as Deka/East Penn and Trojan. They have less to lose/gain by stating that GEL batteries off better cycle life than AGM and Trojan and Deka are at least honest about it.

You can disagree with my observations all you want. I come at this from the perspective of a marine electrician who works on lots of boats not just an n=1 or n=a few.

In the real world of marine installations I see properly installed & charged GELS consistently outlast all the AGM brands..

I have one customer with a Tartan 4100 that is a 1998 boat. His GEL batteries (East Penn) are still going strong in 2012 at 14 years old. 14 year old AGM's? Never seen them in a boat......

I install Odyssey, Lifeline, Deka, Rolls, Trojan, Full River, US Battery, Crown, Superior and others and the GELS consistently outlast all the AGM's including the Odyssey & Lifeline batteries. I currently have a bank of four PC2150's showing about 80% of new capacity at just four years old. This bank has an alt capable of 35% of "C" and is properly programmed for the exact profile Odyssey wants. Not bad, but also not GEL...

Odyssey rates their AGM's (laboratory ratings) at 400 cycles to 80% DOD. Deka/East Penn make both AGM and GEL and rate their GEL batteries at more than double the cycle life of their AGM batteries..

What I see, measure and work with in the real world is that GEL batteries outlast AGM easily and consistently time after time. They appear far more tolerant of less than "full charges" than any of the AGM's. The Tartan 4100 only got solar this year and the boat has been on a mooring since 2004. The GEL batteries have still survived that abuse.

Interestingly enough I don't see much life cycle difference between Lifeline and the Deka product but the Lifeline CAN be equalized/conditioned making it the better value IMHO. Course this relies on owners who know how & when to do this, which most don't, and who actually do it, which most don't. Often by the time I get called in the batteries are expensive plastic boxes filled scrap metal..

Both AGM & GEL need proper charging or they will both die ahead of inexpensive flooded cells. I've yet to see many boats that can supply the 40% / "C" in current that Odyssey wants and many can't even supply the 20% minimum Lifeline wants to see.

That said I do really like the Odyssey AGM's but they need to be installed as a "system" and it can easily push 4k by the time you are done with a new charger, alt, temp sensors serpentine or dual pulley kit etc. etc. etc......

The average life I see on most AGM's, here in Maine where boats are mooring sailed, is 3-4 years. I can greatly extend that with solar and wind but without it they don't even last as long as inexpensive wet cells..

I will be replacing a three year old bank of Lifeline 4D's on a J-42 in the spring because he has no solar and killed them they were technically dead in September but we are holding off until spring....


The best I can do is share my real world experiences and data (I use Midtronics and Argus analyzers as well as Carbon pile load and 20 hour capacity testing). There are definitely benefits to AGM batteries I just don't find cycle life to be one of them.


Trojan has this to say, and they also sell GEL & AGM batteries:

"Gel batteries are more suitable for deep cycling applications whereasAGM batteries are more for light cycling and engine-starting applications."






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Old 04-12-2012, 09:48   #18
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Re: Need new Gel Batteries in Florida

How do the Gel batteries compare to AGM in accepting a high charge rate?
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Old 04-12-2012, 09:49   #19
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Re: Need new Gel Batteries in Florida

Being able to charge faster is of great value to me
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Old 04-12-2012, 10:01   #20
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Re: Need new Gel Batteries in Florida

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Being able to charge faster is of great value to me
They can usually accept more than many sail boats can supply. Deka claims their GELS can be charged from 0% to 90% of capacity in 3.5 hours. This equates to about 40-50% acceptance..

40% acceptance on a 400Ah bank is an alt that can deliver 160A when hot..... The big thing I see with GELS is that the acceptance rates stay pretty steady for a long while. As an AGM sulfates the acceptance rate can drop off.
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Old 04-12-2012, 10:07   #21
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Re: Need new Gel Batteries in Florida

I did not realize AGMs could sulfate I had a AGMs on my last boat and set it up with a large charger and large alt. Now working out the kinks in my new to me boat. Thinking about new 8 ds I have 7 of them
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Old 04-12-2012, 10:16   #22
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Re: Need new Gel Batteries in Florida

Bob, I'd have to agree with Maine on this one. Even Deka publish specs showing their gels are far better than their AGMs, if they are given the right care. Offhand I think the Deka distributor closest to Miami is American Battery up near marina mile in Fort Lauderdale, but every time battery price comes up it seems that Sams's Club blows everyone away if they can get what is needed.

I HAD Deka's technical booklet in my hands last night while scanning a batch of papers, but decided not to cut it apart to feed it into the scanner. My bad. Should be available online though, with the numbers for both AGM and gel in it.
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