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Firefly Carbon Foam AGM batteries

Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
It is time to replace those old 4d batteries that came with my boat. I recently read about Firefly Carbon Foam batteries. Does anyone have any experience with these? They are a type of Lead acid AGM battery that has some really favorable characteristics. I wonder if I can use my existing charger setup with a Carbon Foam battery. If so, would I just use the AGM charger setting? This question also applies to my solar MPPT controller as well. Can Carbon foam batteries be connected to the alternator output like a conventional battery? Ideally, I would like to use Carbon Foam for my house batteries and a regular AGM for a starter battery. Can these types be mixed in this way?
 
Feb 6, 1998
11,294
Canadian Sailcraft 36T Casco Bay, ME
It is time to replace those old 4d batteries that came with my boat. I recently read about Firefly Carbon Foam batteries. Does anyone have any experience with these? They are a type of Lead acid AGM battery that has some really favorable characteristics. I wonder if I can use my existing charger setup with a Carbon Foam battery. If so, would I just use the AGM charger setting? This question also applies to my solar MPPT controller as well. Can Carbon foam batteries be connected to the alternator output like a conventional battery? Ideally, I would like to use Carbon Foam for my house batteries and a regular AGM for a starter battery. Can these types be mixed in this way?

As one of the first marine installers in the US I can tell you that every bank we've installed still has at least 97% of it's original Ah capacity. I cannot say that about any battery other than LiFePO4.. They do however need proper charging. You will need 14.4V absorption and 13.2V - 13.4V float (13.2V is better for float). You'll also need temp compensation for all charging sources including solar, alternator and battery chargers. At least one of your charge sources should be able to achieve at least .3C (30% of Ah capacity) but .4C (40% of Ah capacity in charge current) is preferred. Whether they can be charged in parallel will be based on the start batteries charge parameters. They also suck a lot of power from an alt, and can burn them up, so an externally regulated alternator system is really the best way to deal with this.
 
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Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
As one of the first marine installers in the US I can tell you that every bank we've installed still has at least 97% of it's original Ah capacity. I cannot say that about any battery other than LiFePO4.. They do however need proper charging. You will need 14.4V absorption and 13.2V - 13.4V float (13.2V is better for float). You'll also need temp compensation for all charging sources including solar, alternator and battery chargers. At least one of your charge sources should be able to achieve at least .3C (30% of Ah capacity) but .4C (40% of Ah capacity in charge current) is preferred. Whether they can be charged in parallel will be based on the start batteries charge parameters. They also suck a lot of power from an alt, and can burn them up, so an externally regulated alternator system is really the best way to deal with this.
Thank you for your quick reply. My issue with Li batteries is that I believe that I need to isolate the Li house battery from the Pb house battery using a battery to battery charger. My thinking is that, on one hand, I would not be able to use the Li battery to start my engine should the starter battery fail and I would not be able to power my VHF etc should my house battery fail, on the other hand. So I would have to remove my 1,2, both battery switch.
 
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Dec 4, 2018
46
Balboa 27 Denver
Oh brother, lots of learning to do here.. Oh, where to start. First recommendation is to go to HowTo, and read for a couple weeks and then come back here.. for more questions. One two switches are not in favor for a variety of reasons and B2B or equivalent are the best approach.
 
Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
Anyway, my question is about Firefly Carbon Foam AGM batteries. Anyone with any experience with them?
 
Feb 26, 2004
21,312
Catalina 34 224 Maple Bay, BC, Canada
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Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
Dec 4, 2018
46
Balboa 27 Denver
Was there something you didn't understand about the reply from Mailsail? seem pretty definitive to me. We have three in our 42 Ft steel gaff schooner and are close to a year in. Primary solar and balmar engine charging have been good so far. Hope to cycle them this winter according to the recommendations and put back in service in the spring.
 
Feb 26, 2004
21,312
Catalina 34 224 Maple Bay, BC, Canada
Thank you, that is extremely helpful
You're very welcome. I've found that reading more than one boating forum expands your vocabulary. :)

I also noted, in a thread about this same subject on another forum:
Please recognize that that discussion veers off into a lot of tangents, some of which are helpful, and some are just dead wrong. An example is how the Balmar external regulators work, i.e., timers or voltage checks. Another is using solar first and then a generator later in the day [one should use the generator for bulk charge first]. And also that those guys are discussing real "out there" cruisers, not one week a year folks.
 
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Apr 8, 2011
290
Hunter 36 Deale, MD
There's a fair amount posted here on SBO regarding Fireflies. Very positive has been my read. I've had them aboard for almost a full season and very happy with them. But as MaineSail pointed out, make sure your charging system is up to the requirements. Older shore chargers (and many new ones) and internally regulated alternators will not charge them properly. I replaced two old 4D batteries with two Fireflies and also upgraded my alternator and shore charger. It makes the upgrade significantly more expensive than just upgrading batteries, but the PSOC capability of the Fireflies made it worthwhile.
 
Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
Was there something you didn't understand about the reply from Mailsail? seem pretty definitive to me. We have three in our 42 Ft steel gaff schooner and are close to a year in. Primary solar and balmar engine charging have been good so far. Hope to cycle them this winter according to the recommendations and put back in service in the spring.
Actually, I did misread mainsail's comments the first time. My apologies. However, my power situation is probably a bit less taxing than some others. Usually, I am at a marina with shore power. I also have solar that is sufficient to recharge batteries when shore power is not available. I take a few trips a season and plan to do some anchoring out. But, as a Great Lakes cruiser, I will likely never need to go for several days without some means of charging my batteries. No ocean crossings for me.

But, I will need to replace my current 2x4d flooded lead acid batteries pretty soon and given the alternatives, the Carbon foam AGMs look attractive. My power needs are really not that intense. I figure, while anchored out, 10 amps to run my CPAP machine, anchor light, refrigerator, cabin lights and a fan or two. Otherwise during the daytime I have solar when sailing or my alternator when motoring or shore power at the marina.

If I have to replace my current charging system and/or add other hardware, then the Fireflys are no longer an attractive option. I am sure that the exact charging specifications Mainsail mentioned are optimal. But, I wonder if, given my less arduous requirements, I can make my current equipment do. My current chargers (both shore power and MPPT) have settings for flooded, AGM, gel and Lithium batteries and my alternator is a typically regulated one. Are these batteries really that intolerant of slightly "wrong" settings? If my choice is to totally rewire my 12v system, I would prefer to stick to conventional batteries. But, if i can get most of the promised performance out of the Fireflys, without redesigning my 12 volt system, then they make economic sense to me.

Also, I wanted to get a sense of sailor's actual experience with these, rather just the expertise of people that are professionals. I guess you could say that I am trying to not "let the perfect be the enemy of the good."
 
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Feb 26, 2004
21,312
Catalina 34 224 Maple Bay, BC, Canada
If I have to replace my current charging system and/or add other hardware, then the Fireflys are no longer an attractive option.
i wrote this to the parallel thread on our C34 forum:

1. How you use your boat: day-sailor, marina hopper, or regular long-duration cruiser/anchor-out. Do you get to plug in reasonably often or not?
2. Your energy budget: without a fridge, but with an Engel, it will most likely be less than 100 ah per day.

Based on all the information in the Electrical systems 101 Topic, I believe you are heading in the wrong direction and doing it backwards.

Your major issue is NOT what technology you use to store the energy, but rather the production and electrical distribution system.

By switching to Firefly batteries, you will increase the demand on your production because of the higher acceptance of those batteries. Your system will not support it.

In terms of priorities, what you should do to improve your system is to first remove the AO from the switch and move it to the house bank. Either buy a combiner or use the B on your switch to charge the reserve or start bank. The "Why" of this is already explained in the Electrical systems 101 Topic.

Then add your solar, and increase your AO with a new alternator and external regulator. Resize your AO wiring to suit.

Only then consider changing battery technology. I don't think you need anything more than wet cells, whether it's 12V or golf carts.

Much depends on how you use your boat, but regardless of that answer you have to improve your production and distribution system first before you can even begin to obtain any storage advantages. As you said, only a single cruise a year doesn't justify all this.
 

KZW

.
May 17, 2014
722
Catalina 310 #307 Bluewater Bay, FL
My two cents. Given your modest requirements, I think the most cost-affective way to go is buy four deep discharge golf cart batteries (extensively discussed in other posts on this forum) and use your existing charger / solar cells / alternator.
I shall now be quiet and gocolor
 
Apr 8, 2011
290
Hunter 36 Deale, MD
Actually, I did misread mainsail's comments the first time. My apologies. However, my power situation is probably a bit less taxing than some others. Usually, I am at a marina with shore power. I also have solar that is sufficient to recharge batteries when shore power is not available. I take a few trips a season and plan to do some anchoring out. But, as a Great Lakes cruiser, I will likely never need to go for several days without some means of charging my batteries. No ocean crossings for me.

But, I will need to replace my current 2x4d flooded lead acid batteries pretty soon and given the alternatives, the Carbon foam AGMs look attractive. My power needs are really not that intense. I figure, while anchored out, 10 amps to run my CPAP machine, anchor light, refrigerator, cabin lights and a fan or two. Otherwise during the daytime I have solar when sailing or my alternator when motoring or shore power at the marina.

If I have to replace my current charging system and/or add other hardware, then the Fireflys are no longer an attractive option. I am sure that the exact charging specifications Mainsail mentioned are optimal. But, I wonder if, given my less arduous requirements, I can make my current equipment do. My current chargers (both shore power and MPPT) have settings for flooded, AGM, gel and Lithium batteries and my alternator is a typically regulated one. Are these batteries really that intolerant of slightly "wrong" settings? If my choice is to totally rewire my 12v system, I would prefer to stick to conventional batteries. But, if i can get most of the promised performance out of the Fireflys, without redesigning my 12 volt system, then they make economic sense to me.

Also, I wanted to get a sense of sailor's actual experience with these, rather just the expertise of people that are professionals. I guess you could say that I am trying to not "let the perfect be the enemy of the good."
Your "less arduous requirements" have no bearing on how you need to charge the Fireflies. They require a specific voltage to be properly charged and maintained, so whether you use them occasionally for a daysail, or frequently for multi-day cruising, you'll need to make sure you charge them at the proper voltages and maintain the proper float charge or you risk damaging your expensive new batteries. Also, your warranty will likely be voided. That said, check the settings on your shore charger - if a preset setting matches what the Fireflies need then you're probably fine. I'd bet that your alternator, however, won't be. That alone means you won't get "most of the promised performance out of the Fireflys" if you're doing any cruising. If you're recharging at the dock every day you'll likely have no problem, as long as your alternator isn't providing over voltage to the batteries. But I tend to agree with the other folks who say your needs likely don't warrant the Firefly batteries, and your charging system would work optimally with something its already set up to do. They're great batteries, but unless you intend to take advantage of the partial-state-of-charge capability they offer, then their expense probably isn't warranted.
 

JRT

.
Feb 14, 2017
1,840
Catalina 310 211 Lake Guntersville, AL
Sounds like you have a upgraded charger then what came with the boat. Do you know what it is and can post that info? Do you know if your alternator is original with built in regulator? If it is I would stick with Golf cart batteries and spend the extra boat bucks on a upgrade.
 
Aug 21, 2019
54
Catalina 315 Grosse Pointe Park, MI
The good news is that I have until Spring to figure all this out. I don't like my current 4d batteries because they are big, heavy, tend to leak when the boat heels over and are surprisingly expensive, all things considered. Replacing them with batteries with similar issues is also undesirable. In any case my new batteries will need to fit within the current battery boxes. From what I see advertised on Amazon, I do not think 4 6v golf cart batteries will fit in the available space. I could simply get 3 type 31 AGM batteries. But, for not too much more money, I can get a greater capacity with other alternatives that are smaller, lighter and last longer. As for what I "need," well all things being equal, fewer, smaller, lighter, longer lasting batteries are better than more, bigger, heavier batteries that I have to charge and replace more often. There is not much on my sailboat that I actually "need." Somedays I wonder if I "need" a sailboat at all.

I hear that if I simply connect the Fireflys, as I would other Lead acid batteries, I risk ruining my alternator and only getting a short life out of them. The impression I have gotten, from has been written in this thread, is that these batteries are just as picky as Lithium batteries. But, I wonder, how tolerant these batteries really are to inaccurate charging? Unfortunately, I do not get a sense of this from what I have researched or seen in this forum so far. The unit to unit output of real world battery chargers varies to some degree. I doubt if batches of actual batteries are identical. There certainly has to be some leeway, otherwise these batteries would be totally useless in practice.

So I wonder, what is the cost of a mismatch between the stated charging requirements and the real world consequences of them? Would they really kill my alternator? If it is just a matter losing 10% of the life of the battery by using the baked in settings of my current charger(s) and occasionally allowing the alternator to charge them? In that case, Firefly batteries would still be highly attractive. If the Fireflys are really no more tolerant than Lithium batteries, I see no advantage to them. I would still have to isolate my house from my starter battery in either case. If that is true, I just see no point to buying them, since Lithium batteries have come way down in price.

Vendors like to sell expensive equipment and much of the information comes from these same vendors. In my 16 years owning a sailboat I have learned, the hard way, that one is well served by a bit of scepticism. Marine equipment is expensive; I do not want to replace perfectly functioning equipment. There is no limit to the amount of money a boat can absorb.
 
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JRT

.
Feb 14, 2017
1,840
Catalina 310 211 Lake Guntersville, AL
Several 310s have gone 4 GC batteries in the space. This thread is the great job my previous owner did with new charger, 4 GC a stand alone 12v starting battery wiring and a smart cord shore power upgrade. It works great and the only weakness is the alternator but we just day sail.

 

leo310

.
Dec 15, 2006
317
Catalina Catlina 310 Campbell River BC
We have 4 GC batteries plus 1 12 volt starter battery. The only thing that we also have is 330 watts of solar, with this set up we can stay at anchor for weeks with out running engine to charge the house banks. During the day we use a 2000 watt inverter to charge our laptops or any other devices that require 110 volts and so far we never get lower that 90% on the batteries. BTW our battery banks are over 5 years old.
 
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Tom J

.
Sep 30, 2008
1,691
Catalina 310 Quincy, MA
We have 4 GC batteries plus 1 12 volt starter battery. The only thing that we also have is 330 watts of solar, with this set up we can stay at anchor for weeks with out running engine to charge the house banks. During the day we use a 2000 watt inverter to charge our laptops or any other devices that require 110 volts and so far we never get lower that 90% on the batteries. BTW our battery banks are over 5 years old.
We have the same setup, and it works fine for us. I have even given up using the onboard battery charger when we are on shore power. The solar controller does a better job of keeping the 4 GC's charged.
 
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