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Old 19-06-2023, 00:42   #1
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Cycle chart for West Marine AGMS?

Hi,

I just bought three new size 24 dual purpose 12v batteries from West Marine to replace my old batteries. I was wondering what a good rule for minimum SOC to hit before recharging to maximize battery life would be. Trying to make these last. My demands are very limited. I go out mostly for day trips or for once-a-month average overnight trips, no AC, no fridge. I have about 240 AH on the house bank. I may buy a plug-in inverter to charge laptops. I am also going to set-up a solar power system shortly. I should be able to keep them very close to fully charged most times. What is is good rule of thumb for an SOC to stop at?
thanks!
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Old 19-06-2023, 00:56   #2
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Re: Cycle chart for West Marine AGMS?

Following as these will likely be what I use when I replace my current AGMs
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Old 19-06-2023, 01:32   #3
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Re: Cycle chart for West Marine AGMS?

Zac, you will find that the a ball park figure of 50% discharge is the recommended limit. However, be aware nothing fatal happens if you go to 49% or even deeper occasionally. The most important thing with AGMs is to ensure they are swiftly charged back up again to 100%. The AGMs should give you the recommended absorption and float volt setting on the battery.

I have a pair of Trojan 24s that sit on float 6 days week twiddling their thumbs enjoying life and have been for 6 years.

Equally that doesn't mean charge to 100% and stop, but 100% and a nice long absorption as well.

Your plan to install solar is good and depending on the panel you could use a PWM solar controller, but make sure its a genuine one, not some cheap Chinese on / off type. Or if you are feeling flush a MPPT, again check that its a genuine one. I suspect for float charging your AGMs whilst you are not using the boat, a 50w solar panel will do. Alternatively a 100w solar panel will generate 5Ah in good sunshine and really start to charge them back up if they are flat. Depends on budget and real estate to mount them.

Hard glass framed panels in a marine environment may last some years. Semi flexible may not so if you use them, you may have to accept perhaps a 5 year life.

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Old 19-06-2023, 01:36   #4
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Re: Cycle chart for West Marine AGMS?

Quote:
Originally Posted by Letterkenny View Post
Following as these will likely be what I use when I replace my current AGMs
AGMs are not great house batteries and you are paying for a design you probably can't use like fast charging and discharging.

Thicker plate batteries for deep cycling will last longer, at a price. I have an AGM for engine start, but won't use them for the domestic batteries. Zac already has them and is likely a low power user, so perhaps not so critical. However, on a 35ft Jenny with lots of electronics you might benefit from choosing another type, like flooded lead acid.

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Old 19-06-2023, 05:31   #5
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Re: Cycle chart for West Marine AGMS?

Quote:
Originally Posted by zachduckworth View Post
I just bought three new size 24 dual purpose 12v batteries from West Marine to replace my old batteries. I was wondering what a good rule for minimum SOC to hit before recharging to maximize battery life would be. Trying to make these last. My demands are very limited. I go out mostly for day trips or for once-a-month average overnight trips, no AC, no fridge. I have about 240 AH on the house bank. I may buy a plug-in inverter to charge laptops. I am also going to set-up a solar power system shortly. I should be able to keep them very close to fully charged most times. What is is good rule of thumb for an SOC to stop at?
Many lead-acid (including AGM) battery makers suggest 50% DoD for longest life. West Marine batteries may be made by East Penn/Deka or one of the others... so you might be able to find the same battery on the maker's site... and from that, you may be able to find a relevant life cycle chart.

You can probably also find there the maker's recommendations for specific bulk, absorption, and float voltages... and then set your charger to those, or as close to those as possible.

Sounds like your usage is light enough so you can just plug back into shorepower (with charger) after a day sail or overnight anchor... and call it good.

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Old 19-06-2023, 05:47   #6
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Re: Cycle chart for West Marine AGMS?

Unless things have changed, the West Marine batteries are East Penn / Deka, so the info for those should match the WM stuff. In my opinion, they're not great deep cycles, but those AGMs have given great service over the years as starting batteries. The pair that start my engines are ~6 years old now and not showing any signs of getting weak.
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Old 19-06-2023, 05:48   #7
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Re: Cycle chart for West Marine AGMS?

For less than half the cost of three West Marine dual purpose Group 24 AGM batteries, you could buy two GC2 golf batteries and have a far superior house bank. And they will probably last twice as long.
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Old 19-06-2023, 06:35   #8
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Re: Cycle chart for West Marine AGMS?

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Originally Posted by rslifkin View Post
Unless things have changed, the West Marine batteries are East Penn / Deka, so the info for those should match the WM stuff. In my opinion, they're not great deep cycles, but those AGMs have given great service over the years as starting batteries. The pair that start my engines are ~6 years old now and not showing any signs of getting weak.
Actually the are only two or three companies making lead acid batteries and they just relabel them for whatever store they go to. Doesn't matter where you buy them except for price.
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Old 19-06-2023, 07:08   #9
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Re: Cycle chart for West Marine AGMS?

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Actually the are only two or three companies making lead acid batteries and they just relabel them for whatever store they go to. Doesn't matter where you buy them except for price.
There are more than 3 manufacturers. The big ones I know of that manufacture (not just re-label) lead acid batteries of various types are: East Penn, Johnson Controls (makes quite a few brands), Exide, Rolls, Crown, Fullriver (AGM and gel only, they don't make flooded batteries), US Battery, Enersys (Odyssey, Northstar, and X2 power brands).
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Old 19-06-2023, 07:23   #10
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Re: Cycle chart for West Marine AGMS?

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There are more than 3 manufacturers. The big ones I know of that manufacture (not just re-label) lead acid batteries of various types are: East Penn, Johnson Controls (makes quite a few brands), Exide, Rolls, Crown, Fullriver (AGM and gel only, they don't make flooded batteries), US Battery, Enersys (Odyssey, Northstar, and X2 power brands).
You missed Concorde (aka Lifeline)
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Old 19-06-2023, 07:26   #11
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Re: Cycle chart for West Marine AGMS?

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You missed Concorde (aka Lifeline)
Good catch! I knew I would miss at least one in there. Only a couple of those manufacturers build the bulk of the common labels you see in stores, but there are certainly quite a few others out there building batteries.
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Old 19-06-2023, 10:38   #12
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Re: Cycle chart for West Marine AGMS?

Quote:
Originally Posted by Pete7 View Post
AGMs are not great house batteries and you are paying for a design you probably can't use like fast charging and discharging.

Thicker plate batteries for deep cycling will last longer, at a price. I have an AGM for engine start, but won't use them for the domestic batteries. Zac already has them and is likely a low power user, so perhaps not so critical. However, on a 35ft Jenny with lots of electronics you might benefit from choosing another type, like flooded lead acid.

Pete
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Old 19-06-2023, 12:47   #13
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Re: Cycle chart for West Marine AGMS?

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Originally Posted by zachduckworth View Post
. What is is good rule of thumb for an SOC to stop at?
100%

really, it mean it
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Old 19-06-2023, 23:41   #14
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Re: Cycle chart for West Marine AGMS?

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Originally Posted by JimsCAL View Post
For less than half the cost of three West Marine dual purpose Group 24 AGM batteries, you could buy two GC2 golf batteries and have a far superior house bank. And they will probably last twice as long.
Interesting. I'll have to look into this in the future. Everything is practice for the next boat.

As a few people pointed out, my power needs are pretty limited. I'm excited to get a completely new set of battery equipment that I'll know well. My old system is all 1990s era technology, so this system will catch me up more than twenty years worth of technology, plus I'll have nice, fresh batteries. And I'm re-rigging how they're installed to make them more secure. They're all clamped in place now with zero wiggle movement. Really looking forward to the solar as well. So far the project has been pleasantly low drama. It'll be an entirely re-wired boat when I'm finished.
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Old 20-06-2023, 00:46   #15
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Re: Cycle chart for West Marine AGMS?

Cycle between 50% and 100%.

Yes there are better choices for house batteries. For AGM, Lifeline would be the prima candidate (they invented it). For Gel, Sonnenschein is the top performer (they invented it). But all those are blown away by LiFePO4.

For start batteries I keep it at AGM, with the Odyssey TPPL range being the ultimate and one of the few with milspec ratings and being used by coastguards and even armored vehicles etc.
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