Time for new battery bank - Prefer AGM this time around.

[Caleb C]

Hi Friends,

Time to replace our 4 6v-370ah flooded cell battery banks.
We're not going lithium, but would like AGM for less maintenance.
Been searching online and so far it appears that I have a couple choices:

1. 260ah Mastervolt AGM - They will fit in current battery tray.
2. 400ah Mastervolt AGM - Their height won't fit in current battery tray.

So here's my question: What other choices do I have? Can I get THICK plate AGM batteries that are closer to my current 370ah capacity and still fit within the battery tray. Buying 4 of them.

We charge our batteries via: engine alternator, 370 watt solar panel with 30amp MPPT charge controller, and the 5500 watt generator.

Thanks for suggestions and/or links to appropriate battery sources.

[Paul L]

Consider the Firefly batteries. Have some nice advantages over standard AGMs. They are carbon foam AGM
https://www.bruceschwab.com/advanced...asis-group-31/

[Smokeys Kitchen]

Two other possibilities are Lifeline - which we have and like - and of course Rolls. Our Lifelines are fairly short and those might work for you. 250 AH each, so similar to the Mastervolts. I do not know the current prices on either but have heard the Rolls are more expensive.

Imagine that!

[ranger58sb]

Originally Posted by Caleb C

Hi Friends,

Time to replace our 4 6v-370ah flooded cell battery banks.
We're not going lithium, but would like AGM for less maintenance.
Been searching online and so far it appears that I have a couple choices:

1. 260ah Mastervolt AGM - They will fit in current battery tray.
2. 400ah Mastervolt AGM - Their height won't fit in current battery tray.

So here's my question: What other choices do I have? Can I get THICK plate AGM batteries that are closer to my current 370ah capacity and still fit within the battery tray. Buying 4 of them.

370-Ah each battery? So 370-Ah for each 6V pair at 12V? 740-Ah total capacity on that one bank?

Lifeline makes some 6V AGM options that are taller and with more capacity than their GC2 equivalent. Their GPL-6CTs are 300-Ah each, and their GPL-L16Ts are 400-Ah each.

-Chris

[zboss]

Do AGM’s even need to be in a battery tray or is the requirement just that they don’t move...? The point being... if they just don’t have to move that’s generally an easy fix and opens up the possibility of using a wider range of battery sizes.

[Caleb C]

Originally Posted by zboss

Do AGM’s even need to be in a battery tray or is the requirement just that they don’t move...? The point being... if they just don’t have to move that’s generally an easy fix and opens up the possibility of using a wider range of battery sizes.

In our engine room there is a tray for house batteries under the tray for starting battery and inverter /charger system. So batteries need to fit in an area where 480 pounds of batteries don't fly around the engine room on a wrinkled ocean.

[missourisailor]

Originally Posted by Paul L

Consider the Firefly batteries. Have some nice advantages over standard AGMs. They are carbon foam AGM
https://www.bruceschwab.com/advanced...asis-group-31/

^^+1

If they fit, will run circles around other AGM's.
And for same capacity, half of total Ah are needed.

[Suijin]

Originally Posted by missourisailor

^^+1

If they fit, will run circles around other AGM's.
And for same capacity, half of total Ah are needed.

I would not count on that, going with half the AH capacity. They are new tech and while they have a remarkable record of coming back to near 100% after deep discharge and general abuse, no one knows what the late life scenario for them is as none of them are old enough yet to have gone through it. If you eventually start to see a decline in performance you don't want to be stuck with half the AH that you need.

If they don't have a late life change in performance then they are magic. Or maybe they just fail catastrophically.

[Stu Jackson]

Caleb,

Less maintenance, yes. But, do you have the charging capabilities needed to support them? Do you still have a Hitachi alternator on your engine?

You may have seen these before, if not, you should go through them. Good luck in your hunting.

AGM Batteries - Making The Choice (from Maine Sail)

https://forums.sailboatowners.com/in...choice.124973/

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
https://forums.sailboatowners.com/in...teries.133773/

Additional Observations on the Limits of AGMs Electrical Systems 101

[zboss]

Originally Posted by Suijin

I would not count on that, going with half the AH capacity. They are new tech and while they have a remarkable record of coming back to near 100% after deep discharge and general abuse, no one knows what the late life scenario for them is as none of them are old enough yet to have gone through it. If you eventually start to see a decline in performance you don't want to be stuck with half the AH that you need.



If they don't have a late life change in performance then they are magic. Or maybe they just fail catastrophically.

I expect them to drop off a cliff but that cliff is a long long ways away. The firefly warranty is 2 year @ 100% and then prorated for an additional 4 years.

What is interesting is that the warranty language says the warranty is based on a fixed number of Ah that can be expected to be withdrawn from the battery in its lifetime, in addition to the limits above. However, they fail to mention what that number of Ah are.

[Paul L]

Originally Posted by zboss

I expect them to drop off a cliff but that cliff is a long long ways away. The firefly warranty is 2 year @ 100% and then prorated for an additional 4 years.

What is interesting is that the warranty language says the warranty is based on a fixed number of Ah that can be expected to be withdrawn from the battery in its lifetime, in addition to the limits above. However, they fail to mention what that number of Ah are.

A 6 year warranty is pretty darn good for a marine installation. That is an interesting clause about the max amp hours.

[wrwakefield]

Caleb,

If you are considering AGMs only to reduce battery maintenance [which I assume means topping up with water...] have you considered a single point watering system for a bank of flooded lead-acid [FLA] batteries?

That is what we did because our house batteries are not readily accessable. It was far more cost effective to buy new FLA batteries and a watering system [~US$200 for a bank of 8- 6 VDC batteries] than replace the bank with AGMs.

Watering them all [without accessing them...] takes less than a minute- including getting the jug of distilled water and hose, and stowing it all when finished.

I have photos and links on our page about our house bank if you are interested.

Best wishes finding what is best for your needs.

Cheers! Bill

[FlyingScot]

Originally Posted by Paul L

Consider the Firefly batteries. Have some nice advantages over standard AGMs. They are carbon foam AGM
https://www.bruceschwab.com/advanced...asis-group-31/

Thanks for the link. Nigel Calder seems to have a very positive initial feeling about these batteries.

Anyone know of any place that has them in stock?

-Chris

[Dougtiff]

Remember, AGM battery's can be oriented in any attitude other than upside down, in my ast boat, i had them lying om their sides to fit the space.

[CarinaPDX]

Right now you have 740aH@12V - a pretty large capacity. One easy thing to do is simply replace them with the same. If you don't want to modify the battery boxes then the smaller AGMs would give you 400aH@12V - a little more than half of the existing capacity. Can you live with that? If so, then that is a good solution. If not, then you are either back to the original FLA or you must modify the battery boxes. If you are going to modify the battery boxes I would recommend that you switch to more common BCI or DIN battery sizes (ideally you would design the boxes to closely fit one BCI size and one DIN size, so batteries can be found widely).

The current battery size appears to be heavily used in home solar systems because they have very low cost/capacity. I would be surprised if that size is very widely available in the cruising grounds of the world, so for a world cruiser it may be a problem in the future.

I switched from Rolls FLA batteries to Sonnenschein gel batteries years ago. The 25% or so drop in capacity was acceptable to me (the old size was not available in gel), and the "stiffer" voltage was an improvement for using the SSB. (Under heavy loading the voltage drops less than with FLA, causing fewer problems with electronic equipment.) Also, it could accept charge at a higher rate, reducing engine running times for charging. I'm happy with the choice, especially since modern LED lighting and LCD displays use less power than older technology. As always, YMMV.

Greg