Practical Sailor, Firefly AGM Batteries?

Apr 30, 2015
18
36 Sloop 36 Chesapeak Bay
Is anyone here using Firefly AGM batteries? I am interested in learning more about them because they seem to fight off sulphation better. Practical Sailor says they are new to the marine world but look promising. My current bank is dead.
 
May 10, 2008
392
Catalina 355 Boston
Is anyone here using Firefly AGM batteries? I am interested in learning more about them because they seem to fight off sulphation better. Practical Sailor says they are new to the marine world but look promising. My current bank is dead.
That article was written by our very own Maine Sail, so I'm sure he has some perspective. Another outstanding piece of work Maine Sail!
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
Is anyone here using Firefly AGM batteries? I am interested in learning more about them because they seem to fight off sulphation better. Practical Sailor says they are new to the marine world but look promising. My current bank is dead.
When I get a moment to sit down for a bit longer I can give you some more details.

I can say I am impressed enough to have four sitting in my shop getting installed early next week on a customers boat.. They are very impressive batteries for sure when it comes to fending off damage from sulfation.


I had an opportunity today to have lunch with Kurtis, the Firefly inventor, Nigel and Bruce of Ocean Planet Energy. Lots of deep technical stuff and lots of questions from Nigel & I to Kurtis.

Nigel was very impressed with them on his own boat last year. So much so that he left his own bank of Firefly's at 50% SOC and came home to Maine. His boat is in Scotland and the batteries will have been at 50% SOC for 8 months when he returns in a few weeks. He has faith they will fully recover. If they do, this is really quite game changing for the way we use our batteries on boats. Last year Nigel purposely never charged them to more than 80% SOC and they fully recovered with full capacity at the end of the year before he put her on the hard..
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
Firefly has longer term data but in the marine market there are few out there at this point in time. I think the key take away from that article is that:

Fighting Sulfation In AGM's - Practical Sailor May 2015


  • A) All batteries were treated exactly the same using lab grade test equipment and a temp controlled water-bath.

  • B) They were discharged and charged as we often do on boats thus replicating real world use in a "lab like" environment for closer A to B comparisons.

  • The Firefly was the only battery to survive the testing and recover all of its capacity. Other than the Lithium battery, which was used as a control or benchmark really, the Firefly came out on top. PS's caution as "new technology" is certainly within reason, and I tend to agree with it, but the data still speaks rather strongly for the Firefly as a potential game changer for cycling applications on boats..

  • The way we use batteries on boats is murder to them so having a battery than can recover from the effects of sulfation could be a real game changer and far less complicated than LiFePO4.

  • In just 30 cycles some of the AGM batteries lost between 7% and 30% of their total baseline tested Ah capacity.. Just 30 cycles....! In the real world those 30 cycles would have likely been even more punishing, especially in a hot climate.

  • This brings us to a question we did not delve into and that is; these batteries range in lab rated cycle life from 350 cycles to well in excess of 1000 cycles. What good are these lab numbers, and how realistic are they if we don't use our batteries in a lab like manner? The 350 cycle rated battery lost 30% or 1% for every cycle. I can't talk about the second battery we tested yet other than to say wait for the next issue......
My gut suspicion is that a deep cycle AGM battery (Odyssey, Northstar & Lifeline) really need to get back to 100% SOC every 2nd or 3rd cycle for the best performance and longest cycle life. Ideally every cycle but that is simply not realistic.


It should be noted that the effects of sulfation happen to all lead acid batteries, not just AGM. AGM batteries are just much easier to test and to show how we are murdering our banks by how we use and abuse them..



The Firefly we know can go 30 deep cycles, with full recovery, but I suspect a full recharge ever 15-20 days is more reasonable for that battery. I anxiously await Nigel's email when he gets back to Scotland and cycles & tests his Firefly's after sitting at 50% SOC for 8 months...! He abused these batteries last year and they lost no capacity. My testing was lab simulated real world and Nigel's was real world. The Firefly survived both tests very well.......
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Maine: Nice work on that battery test article in Practical Sailor. Yet another definitive analysis of the technologies boaters rely upon. Now I just need to find out how to make my new Mastervolt charger equalize my new Lifelines...
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
i thought i read you dont have to equalize the agms like you do the flooded ones
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
EXCEPT the Lifelines. They respond to equalization.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
i thought i read you dont have to equalize the agms like you do the flooded ones
In general you don't equalize AGM batteries other than Lifeline. Equalization, and by this I mean a charger with an equalizing option, can work on any lead acid battery but each AGM manufacturer has designed the battery for specific parameters and most have legitimate concerns about "drying" the battery out through equalization/gassing.

My own thoughts on the issue, after years of doing this, are that we destroy our batteries via sulfation. This is usually due to PSOC cycling, long before we'd ruin them with a periodic equalization.

I have cut open numerous dead AGM batteries only to find them still plenty "wet" but destroyed via sulfation. I suspect there is a fine line of absorption voltage vs. PSOC cyclic use but until the manufacturers study this, and tell us what that fine line is, for PSOC operation, we are only guessing at it to arrive at a suitable cycle life.

I can tell you that charging a certain manufacturers AGM 0.2V higher than recommended has resulted in longer cycle life in PSOC cycling operation but I defer to the manufacturer for others doing the same...

The bottom line is that this is an answer best left to your battery maker. I do suggest using the highest allowable charging voltage you possibly can, as that tends to help fight off sulfation.

The only battery that I have seen that does not need equalization/conditioning is the Firefly and Kurtis, the designer/inventor, is quite adamant that this battery not be charged above 14.4V, temp compensated. Instead the Firefly battery is recovered by discharging it to 10.5V - 11V then fully recharging it once or twice. This battery behaves entirely differently than other lead acid batteries when it comes to sulfation recovery and high voltages are not needed just deep discharges followed by a full recharge. This is due to the carbon foam construction..

With AGM batteries full means 0.5% - 0.3% current acceptance at absorption voltage before they can be considered "full". This is .5A to .3A of charge current acceptance, at absorption voltage, on a 100Ah battery.
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
Thanks Maine that makes me comfortable with what I have got on board ... Although I am interested in fire fly batts and will be watching out for more info ....they may well the bridge between lead acid and lifpro bats