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Old 26-08-2020, 21:36   #1
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marine agm vs automotive agm

Is there actually any difference between a marine agm battery and any other agm battery of the same type?
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Old 26-08-2020, 22:02   #2
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Re: marine agm vs automotive agm

The car ones have a good warranty, but generally aren't that cheap.
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Old 27-08-2020, 04:46   #3
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Re: marine agm vs automotive agm

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Originally Posted by Muaddib1116 View Post
Is there actually any difference between a marine agm battery and any other agm battery of the same type?

Generally, yes. Automotive (and marine starting) AGMs are starting batteries.

"Marine AGMs" or "marine "deep cycle" AGMs are usually dual-purpose batteries (i.e., not really deep cycle).

Unless they're Lifelines and maybe a very few others; in Lifeline's case, their "deep cycle" AGMs are deep cycle, different from their starting batteries. Firefly Oasis Carbon Foam AGMs seem to be offering deep cycle capabilities,

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Old 27-08-2020, 05:52   #4
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Re: marine agm vs automotive agm

Ok, but there's nothing special about the battery that is "Marinized"? It's not sealed better or has more corrosion resistant materials or something that makes it "Marine"?
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Old 27-08-2020, 07:37   #5
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Re: marine agm vs automotive agm

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Ok, but there's nothing special about the battery that is "Marinized"? It's not sealed better or has more corrosion resistant materials or something that makes it "Marine"?
No, itís internal plate construction that determines deep cycle or not.
Iíll get arguments on this, but there is no such thing as a ďMarineĒ battery.
Slap a Marine sticker on one and Voila itís marine, then slap a deep cycle / starter sticker on it and now itís a combo deep cycle / starter battery and you can price it higher

Using the Lifeline battery as an example, there is no real difference between the Lifeline ďmarineĒ battery, and their life of aircraft batteries called Concorde batteries. Aircraft batteries tend to be smaller of course, and if they are flooded batteries, the acid is stronger, but the Lifeline AGM is essentially the same as their aircraft battery.
Of course the aircraft battery costs more.

Itís how an individual manufacturer designs and constructs their batteries that make them better or not, back to lifeline, they do many things better like copper alloy terminals and thicker cases and how the interconnect cells, and have a through and very comprehensive manual for instance. Only battery that I know of that publishes a SOC under load chart, so you can tell the SOC when using the battery with just a voltmeter.

Of course you pay heavily for this
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Old 27-08-2020, 07:43   #6
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Re: marine agm vs automotive agm

Ok, great, thanks!
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Old 27-08-2020, 07:44   #7
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Re: marine agm vs automotive agm

However I should bring this up. Deep cycle AGM automotive batteries are rare, I know of very few automotive AGM deep cycle batteries, yellow top Optima is the only one I know of.

In fact deep cycle automotive batteries are pretty much unheard of, they are almost all starter batteries and that’s what makes them not good for a house bank.
However golf cart batteries are not labeled Marine either, and yet are among the very best deep cycle batteries you can get for a house bank in a boat.

So no in my opinion there is no such thing as a Marine battery, that’s labeling and marketing
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Old 27-08-2020, 07:48   #8
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Re: marine agm vs automotive agm

Ok. The battery I'm replacing isn't really a house bank battery, per se. My house bank is a 24v lithium bank, and the battery I'm replacing is a 12v agm that powers the instruments/mfd's (depthsounder, wind, speed, etc.) as well as a 12v outlet. It is set up to be constantly kept charged by the housebank, so it seems to me that it will never really draw down, so starter or deep cycle doesn't matter too much?
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Old 27-08-2020, 08:14   #9
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Re: marine agm vs automotive agm

For that use I would want a good quality automotive AGM.
I have had good luck with Optima Red tops myself. I prefer AGM’s because twice I have had a flooded battery leak and cause damage, once in an airplane and once in a new car.
Not that it’s likely that I’ll ever buy another new car, but back when I did one of the first things I did was take out the OEM battery and replace it with an Optima.

In my opinion your better off with an Optima than some off brand battery that has a Marine sticker slapped on it.

Just reread your post, for that I’d go with a yellow top (deep cycle) it just my belief that deep cycle batteries due to their thicker plates last longer and are more resistant to vibration etc, and you don’t need a huge short duration high amp load.

Or since your all lithium anyway, why not a lithium motorcycle battery? They seem to be very durable and are a drop in replacement for a lead acid battery.

On edit, you could even easily delete that battery if it’s purpose is to supply 12V to instruments, radio etc as you have a 24V bank and install a 24 to 12V convertor. I have one just to stabilize voltage to my sensitive electronics, feed it anything between 8 to 40 V and it outputs 13.8VDC.

On edit, it’s likely that what charges your 12v batteries puts them on float, and of course that means a constant current draw, unless there are devices connected that must always remain on like a fridge for instance, then you can eliminate that constant current drain by using a convertor that will only draw power when ever on of the 12V devices is turned on.
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Old 27-08-2020, 13:58   #10
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Re: marine agm vs automotive agm

Often the 'marine' versions of batteries offer not just the posts for post clamps like Automobiles use, but threaded studs for ring terminals too.

The 'Marine' versions often come with less warranty

Whether there are internal differences is likely highly dependent on the manufacturer, but I think they just do whatever is cheapest and spend more on extra special marketing and sticker design, and executive bonuses.

The prices for automotive starting AGMS have come way down.
Most will say deep cycle on them. I'd not deep cycle them regularly intentionally.
Most drivers who adopt AGM, assign them 'super battery' status even though their CCA and self discharge is not all that much if any better than their flooded counterparts.

The starter battery AGMS I've been asked to charge/inspect were all relatively young, and badly capacity compromised, and did not improve much with a proper absorption voltage duration charge, which usually took 12 hours before amps tapered to prescribed 'full' levels.

I've not heard anything good about Optima recently, until this thread. When they were new, and made in the USA they got a good reputation for longevity.
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Old 27-08-2020, 14:26   #11
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Re: marine agm vs automotive agm

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Is there actually any difference between a marine agm battery and any other agm battery of the same type?
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Old 27-08-2020, 14:29   #12
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Re: marine agm vs automotive agm

There is no such thing as a "marine" battery.

There are a lot of poor quality AGM batteries on the market that call themselves deep cycle marine batteries. Beware of some of the claims.

I use simple method of determining the quality of deep cycle AGM's. Heavy is good. A high quality 12V AGM deep cycle battery will weigh about 0.3 kg per A/h rating. If they weigh less than this, the A/h rating is being exaggerated.
If you don't want the weight, pay the money and go lithium.
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Old 27-08-2020, 14:31   #13
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Re: marine agm vs automotive agm

Can you use lifepo batteries as starter batteries? All of the motorcycle lithium batteries I found were lithium ion.
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Old 27-08-2020, 14:38   #14
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Re: marine agm vs automotive agm

AGM batteries were designed for two functions - standy power for computer data centers or Radio Transmission facilities and large engine start (think CCA). Decide what function you need the battery for and why you want AGM over Lead Acid. New technology is not an answer.

Typically you can buy two quality deep cycle marine lead acid for the price of one quality AGM. And dont forget to ask the maintenance guys at the golf course which type they use in golf carts where daily drain/recharge occurs.
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Old 27-08-2020, 15:07   #15
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Re: marine agm vs automotive agm

The only difference is that marine batteries cost more
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