Agm batteries....who's the best or worst?

[waterman46]

I just replaced my 12 year old 4D Lifelines with new Lifelines. Cheapest I found was at sepbatteries.com.

I seriously considered and investigated wet cells (again) and everytime I come to the same conclusion: I don't want and cannot be a babysitter for my batteries, I want quicker charging, and above all I want the best safety (no gas, no spillage). This favors AGM.

I think the evidence given in this thread previously, shows that there are some AGM's out there that are less robust than Lifeline and I would stay away from those.

[a64pilot]

Originally Posted by Kenomac

Paul,

I was also planning on starting a similar thread today. Next season, I need to replace the battery bank. Which to choose lead acid, AGM or Lithium ion? Does the AGM battery bank charge up any faster than lead acid using a 10kw generator?

Most of the power coming from our generator just seems to be wasted since it takes so long to charge the batteries. Solar isn't really a viable option in our case, since switching to lithium would cost about the same all inclusive. Then the generator will charge those up quickly.

Ken

The biggest advantage to AGMs is that will take a large charge, their appearance rate is high.
Of course along with that big generator you need some kinda of big charger, my 660 AH bank will easily accept my 125 amp charger and my 60 amp charger both for a significant time until they begin to taper off.
The disadvantage of AGM is of course they are less tolerant of partial SOC cycling, they want to be topped off, often.
But your selling right? I'd nurse your bank, I see buying new batteries for the boat I'm selling to be similar to putting on new tires just to sell the car, it's money down the drain. If you have to replace I'd go with Golf Cart batteries and leave the high buck batteries for the next boat.


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[kmacdonald]

Go with lithium. They are not much more than AGM if you already have an external voltage regulator that can be programmed for lithium use. Saves a lot of weight and charges faster.
A 200Ah lithium will replace a 500Ah AGM nicely.

[gamayun]

Originally Posted by ranger42c

There are a boatload of threads about it, with more complete description by experts like MaineSail (and see his own Compass Marine site)...

But the short version is that 6V golf cart batteries are said to be truly deep cycling capable -- by design, with thicker plates -- whereas 12V "deep cycle" batteries are said to more often be "dual purpose" with a "deep cycle" label attached.

-Chris

I did some research into this and to the benefit of others who might be wondering, there's nothing inherently better between a 6V versus a 12V deep cycle battery -- if it's truly a deep cycle battery such as AGM Lifelines; not flooded 12V batteries, which Mainsail calls "impostor or pseudo deep cycle batteries." The only differences between installing two pairs of 6V AGMs in series/parallel compared to a set of 12V in parallel are: weight (12V are much heavier) and size configuration (i.e., the 6V come in a greater variety of heights and widths that might better fit your compartment).

[ranger58sb]

Originally Posted by gamayun

I did some research into this and to the benefit of others who might be wondering, there's nothing inherently better between a 6V versus a 12V deep cycle battery -- if it's truly a deep cycle battery such as AGM Lifelines; not flooded 12V batteries, which Mainsail calls "impostor or pseudo deep cycle batteries." The only differences between installing two pairs of 6V AGMs in series/parallel compared to a set of 12V in parallel are: weight (12V are much heavier) and size configuration (i.e., the 6V come in a greater variety of heights and widths that might better fit your compartment).

That sounds reasonable, too, but I know our specific AGMs are a "thin plate" design, and even though described (by Odyssey) as being OK for many cycles to 80% DoD... the other side of somebody's coin is that thicker plates are also said to be better for deep cycling.

I have no opinion on the differences; don't have enough technical know-how to judge. Hence deference to MaineSail's expertise.

-Chris

[rwidman]

Originally Posted by gamayun

The only differences between installing two pairs of 6V AGMs in series/parallel compared to a set of 12V in parallel are: weight (12V are much heavier) and size configuration (i.e., the 6V come in a greater variety of heights and widths that might better fit your compartment).

The total weight is going to be the same for the same total capacity. Breaking it into two pieces (2 6volt batteries) may make it easier to handle the weight when installing them but at the same time, there are more cables and more points of failure.

[mitiempo]

Originally Posted by rwidman

The total weight is going to be the same for the same total capacity. Breaking it into two pieces (2 6volt batteries) may make it easier to handle the weight when installing them but at the same time, there are more cables and more points of failure.

Yes the weight of 2-12 volt batteries and 2-6 volt golf cart batteries is about the same. But there is a major difference. The 12 volt pair has 6 cells each while the 6 volt pair only have 3 cells each. The main reason the 3 cells weigh about as much as the 6 cells is because the plates are thicker - there is more lead in each cell. Thicker plates are the main reason the 6 volt batteries are much better at cycling as that is the largest determining factor of battery life, all else being equal.

[Akapeterc]

I got a quote on lithium batteries for the same amp hours as my Trojans had and it was some ridiculous price around about $14,000. I went with AGMs


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[HalfHitch]

My German skipper friend recently entered into agreement to purchase lithium batteries from a Florida based company SMART BATTERY. Unaware of how risky it is to wire $$$ to USA based internet company he proceeded. Batteries never delivered. $4k was finally recouped after many months of intervention from State of Florida fraud unit.