Carbon Foam Batteries 1 Year Later

FF said:

"benefits is more elusive, more personal, more situationally-dependent.."

Most of the operational results can be had with a std LA battery bank and a SOC ,state of charge meter ..

An SOC meter is the first item that should be installed on any boat that will overnight with out dock power.

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I have a multi meter hooked into my parallel wired house bank of 4 deep cycle 31 wet cell batts. Check it often while utilizing electricity from batts; also while charging batts. Don't let discharge go beyond 50% before full recharge by one means or another. After full charge (I slightly over charge them) I let batts rest/settle for 30 to 60 minutes with no draw on their energy to check and see if they held a full charge. If not, I will pump more energy into them until they do reach/hold full charge.

To me... lit dial multi meter hooked directly into house bank is simplest most efficient and least costly way to keep close eye on battery charge levels. I also have multi meter in engine compartment for manually checking other batteries... with little need to do so, because they are always kept at full charge by means.

Another hint for simplicity - My house bank readily starts my engines. No need of a starter batt for engines. I do keep independent 27 starter batt on gen set; it charges in two ways... one is solar. Then I have a completely isolated 27 emergency batt in it's own black batt box that sits idle but is kept at 100% charge. This is just incase all else fails I have ready spare. It worked well couple years ago when our tow behind runabout's batt crashed... the new spare batt was quickly installed... and... off we went to play.

Arch said:

After reading about these on a marine electronics review site I thought they might make sense at $426 but with the recent price increase to $486....forgetaboutit.
Just too expensive for me.


Arch

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When looking at Firefly batteries don't forget to include the fact that they are designed and intended for PSOC use to 80% DOD, then cycled back to 80-85% so you are actually using 60-65% of the battery, even when out cruising, vs. just 30-35% with other flooded or AGM batteries.

Also that 80% DOD often chops an entire AGM out of the equation so the $486.00 per battery becomes a much more equivalent deal when you need only three vs. four of the competitors.

The cost of lead acid batteries, not just AGM, can not be judged on the box price alone. Ah capacity, projected cycle life, usable capacity, and lifetime watt hours or Ah's delivered are what will determine actual battery cost over the long haul. Many of my sailboat customers can murder batteries in less than 100 cycles regardless of flooded or AGM and this is due to PSOC use & sulfation.. Many of my trawler customers can murder them in less than 150 cycles for the same reasons. Was on a GB-32 yesterday and the flooded deep cycle Trojan's were sitting at 12.32V when I got on-board. They are three years old and ready for the recycle bin. Why? PSOC abuse.

The box price for Firely is now certainly higher than other premium G-31 AGM's (Lifeline, Odyssey, Northstar) but box price alone does not equate to value.

If you want to consider East Penn a premium AGM please read the May 2015 issue of Practical Sailor and see how they dealt with PSOC abuse.

When you consider that the other batteries should only be cycled to 50% DOD, in order to maximize cycle life, and they don't handle PSOC use nearly as well, it certainly makes a strong case for these batteries not costing as much as they may appear to, when judged only on the per unit price.

For example: (current street price from my distributors)

Three Firefly G-31's = 330Ah - At 80% DOD = 264 Usable Ah's - $486.00 X 3 = $1458.00

Four Lifeline G-31's = 420Ah - At 50% DOD = 210 Usable Ah's - $370.00 X 4 = $1480.00

Four Odyssey G-31's - 400Ah - At 50% DOD = 200 Usable Ah's - $377.00 X 4 = $1508.00

Four Northstar G-31's - 404Ah - At 50% DOD = 202 Usable Ah's - $390.00 X 4 = $1560.00

Also with the Firefly battery at 80% DOD this means you are in the very efficient bulk charge stage (constant current) far longer than if we started at 50% DOD. This means considerably more usable energy can be returned to the bank in a shorter time frame than with an AGM that is only cycled to 50%.

I have a fair number of Firefly banks out there, I even run one on my own boat as a reserve bank, (LiFePO4 primary) and a lot more scheduled to be installed and I can see the value in them for certain types of cruisers...

I still install a lot of Lifeline, Odyssey, Northstar, Trojan, Crown & US Battery etc. too.

I buy my Firefly batteries From Bruce at Ocean Planet Energy but he has a number of distributors throughout the US. If you are in the Chess Coastal Climate Control is also a Firefly dealer.

When Bruce first mentioned the Firefly battery to me I basically called BS on it. I then designed a test protocol to simulate typical marine use that I witness on cruising sailboats to see if it was actually any different than the other AGM's. Unfortunately my assumptions about the Firefly were misguided and wound up eating crow on my BS call...

Partial State of Charge Test May 2015

Partial State of Charge Test August 2015

I believe myself and Nigel have the oldest Firefly's in the marine market and both of these banks have had the living snot beaten out of them. Both Nigel's bank and my own Firefly's still capacity test at 100% of initial tested Ah capacity.

I no of know other battery, flooded or AGM I can say that about. Even GEL batteries don't stand up to the cycling abuse I have thrown at the Firefly's, and GEL's are excellent deep cycling batteries despite needing very careful charging.

Despite only being a few years into Firefly, in the marine market, they definitely do separate themselves from the pack when dealing with a PSOC environment.

For trawlers the reduced weight of additional batteries and PSOC are a bit less of an issue than they are for sailboats, but still can be important for those who cruise regularly.

CMS

Thanks for your post. Any thoughts on footprint comparing Firefly to Trojan T105s? For me, utilizing same battery boxes with more stored power is attractive.

CMS said:

When looking at Firefly batteries don't forget to include the fact that they are designed and intended for PSOC use to 80% DOD, then cycled back to 80-85% so you are actually using 60-65% of the battery, even when out cruising, vs. just 30-35% with other flooded or AGM batteries.

Also that 80% DOD often chops an entire AGM out of the equation so the $486.00 per battery becomes a much more equivalent deal when you need only three vs. four of the competitors.

The cost of lead acid batteries, not just AGM, can not be judged on the box price alone. Ah capacity, projected cycle life, usable capacity, and lifetime watt hours or Ah's delivered are what will determine actual battery cost over the long haul. Many of my sailboat customers can murder batteries in less than 100 cycles regardless of flooded or AGM and this is due to PSOC use & sulfation.. Many of my trawler customers can murder them in less than 150 cycles for the same reasons. Was on a GB-32 yesterday and the flooded deep cycle Trojan's were sitting at 12.32V when I got on-board. They are three years old and ready for the recycle bin. Why? PSOC abuse.

The box price for Firely is now certainly higher than other premium G-31 AGM's (Lifeline, Odyssey, Northstar) but box price alone does not equate to value.

If you want to consider East Penn a premium AGM please read the May 2015 issue of Practical Sailor and see how they dealt with PSOC abuse.

When you consider that the other batteries should only be cycled to 50% DOD, in order to maximize cycle life, and they don't handle PSOC use nearly as well, it certainly makes a strong case for these batteries not costing as much as they may appear to, when judged only on the per unit price.

For example: (current street price from my distributors)

Three Firefly G-31's = 330Ah - At 80% DOD = 264 Usable Ah's - $486.00 X 3 = $1458.00

Four Lifeline G-31's = 420Ah - At 50% DOD = 210 Usable Ah's - $370.00 X 4 = $1480.00

Four Odyssey G-31's - 400Ah - At 50% DOD = 200 Usable Ah's - $377.00 X 4 = $1508.00

Four Northstar G-31's - 404Ah - At 50% DOD = 202 Usable Ah's - $390.00 X 4 = $1560.00

Also with the Firefly battery at 80% DOD this means you are in the very efficient bulk charge stage (constant current) far longer than if we started at 50% DOD. This means considerably more usable energy can be returned to the bank in a shorter time frame than with an AGM that is only cycled to 50%.

I have a fair number of Firefly banks out there, I even run one on my own boat as a reserve bank, (LiFePO4 primary) and a lot more scheduled to be installed and I can see the value in them for certain types of cruisers...

I still install a lot of Lifeline, Odyssey, Northstar, Trojan, Crown & US Battery etc. too.

I buy my Firefly batteries From Bruce at Ocean Planet Energy but he has a number of distributors throughout the US. If you are in the Chess Coastal Climate Control is also a Firefly dealer.

When Bruce first mentioned the Firefly battery to me I basically called BS on it. I then designed a test protocol to simulate typical marine use that I witness on cruising sailboats to see if it was actually any different than the other AGM's. Unfortunately my assumptions about the Firefly were misguided and wound up eating crow on my BS call...

Partial State of Charge Test May 2015

Partial State of Charge Test August 2015

I believe myself and Nigel have the oldest Firefly's in the marine market and both of these banks have had the living snot beaten out of them. Both Nigel's bank and my own Firefly's still capacity test at 100% of initial tested Ah capacity.

I no of know other battery, flooded or AGM I can say that about. Even GEL batteries don't stand up to the cycling abuse I have thrown at the Firefly's, and GEL's are excellent deep cycling batteries despite needing very careful charging.

Despite only being a few years into Firefly, in the marine market, they definitely do separate themselves from the pack when dealing with a PSOC environment.

For trawlers the reduced weight of additional batteries and PSOC are a bit less of an issue than they are for sailboats, but still can be important for those who cruise regularly.

Click to expand...

Ahhh...the voice of logic, expertise, and experience. Thanks for taking the time to share that

sunchaser said:

CMS

Thanks for your post. Any thoughts on footprint comparing Firefly to Trojan T105s? For me, utilizing same battery boxes with more stored power is attractive.

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Unfortunately, for now, the Firefly is only available in a standard Group 31 format. The T105 is a standard GC2 size or about the same foot print as a Group 24 battery, only taller.

The Firefly is not going to be a fit for everyone or every application but if you can take advantage of its benefits, and it fits physically, then it's a good option.

CMS said:

Unfortunately, for now, the Firefly is only available in a standard Group 31 format. The T105 is a standard GC2 size or about the same foot print as a Group 24 battery, only taller.

The Firefly is not going to be a fit for everyone or every application but if you can take advantage of its benefits, and it fits physically, then it's a good option.

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We have Firefly but only a very short time so not a lot of experience with them. We felt the standard Group 31 batteries installed at the factory were inadequate but wanted to improve without making a lot of other changes such as rearranging or adding or rewiring. So, we gambled on Firefly as the simplest solution. They fit physically so were the simplest and most cost effective solution assuming they perform as advertised. Time will tell.

For those who have separate house and starting banks...would one Group 31 Firefly have enough cold cranking oomph to replace a 4D wet cell, or would two be recommended? (Our 100hp engine starts easily, so far, and because of the warming effect of the Pacific Ocean the engine room never goes below freezing even if it's -20C outside.)

This might be where the overall long term cost savings has a bit of a breakdown?

CMS, Thanks for the great post with some very good information. I am a fan of wet cells as they are cheap, simple, known quantity, and I am a cheap and simple guy. However, my house bank batteries are 6 year old sealed wet cells. They are also inconveniently located if I were to replace them with 6v Golf carts. I would need to either install a watering system, or go with a no-watering battery. The most impressive argument you made was the usable Ah.

Hopefully, my current batteries will live for another few years. Then I will be looking at replacing a bunch of batteries and will do a complete re-evaluation of my system. The Fireflies will definitely be in consideration.

The other advantage as far as cost, is that I am seriously considering some solar to help with getting that 10% of full charge on the batteries. Since the Firefly handle PSOC so well, that isn't as important and could save me the time, expense, hassle, and roof-top real estate of installing solar.

dhays said:

The most impressive argument you made was the usable Ah.

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While that is a good argument the one that I really like is the ability to utilize your charge sources considerably more efficiently and effectively by keeping them in bulk/constant current for far longer than an AGM cycled to only to 50% DOD.

Bulk charging is darn near 100% efficient meaning almost every Ah you put in during bulk is removable during discharge. In reality it is up in the 98-99% +/- range for input to output.

When you consider that a standard AGM, such as a healthy Lifeline, when charged at .4C or 40% of Ah capacity, from 50% SOC will only remain in bulk for about 19-20 minutes before attaining absorption voltage the 80% DOD becomes a real game changer in usable capacity to time spent "fast charging".

By cycling to 80% DOD this makes considerably better use of the alternator or large inverter/charger or even multiple chargers.. With a .4C charge rate from 50% SOC (AGM batteries are often bought for their high charge acceptance) this makes the alternator useful for replacing about 13-15% of the bank capacity in bulk before being limited by voltage and seeing your CAR (charge acceptance rate) begin to decline.

By discharging that same battery to 80% DOD we remain in bulk for approx 42-45% of the usable capacity range and make considerably better use of our charge sources full potential, especially if idling the engine or running a genset to push large inverter/chargers to recharge. When cycling to only 50%, with a high charge rate such as .4C, your CAR begins declining in the mid to low 60-65% SOC range.

So charging for an hour from 80% DOD with a .4C sized alternator yields nearly everything you put in that can now be removed in usable energy. Almost none of that hour was wasted by a declining charge efficiency & declining CAR.. From 50% DOD you don't get nearly as much usable energy out of that hour of fuel....

CMS said:

For example: (current street price from my distributors)

Three Firefly G-31's = 330Ah - At 80% DOD = 264 Usable Ah's - $486.00 X 3 = $1458.00

Four Lifeline G-31's = 420Ah - At 50% DOD = 210 Usable Ah's - $370.00 X 4 = $1480.00

Four Odyssey G-31's - 400Ah - At 50% DOD = 200 Usable Ah's - $377.00 X 4 = $1508.00

Four Northstar G-31's - 404Ah - At 50% DOD = 202 Usable Ah's - $390.00 X 4 = $1560.00

Click to expand...

Extending this a little...

I've been considering -- bordering on actual planning -- to change our starboard bank from 3xG31s to 4xGCs whenever the current AGMs bite the dust. These would be for starting one engine, running half the house load, and running electronics suite on the bridge.

At first glance, that looks like ~300 Ah for the 3xG31 bank, versus ~440 Ah for the golf cart bank.

With most AGMs, that would look like:
- 300 Ah @ 50% SOC = 150 Ah routinely usable
- 440 Ah @ 50% SOC = 220 Ah routinelyusable

OTOH, 3x 12V Fireflies in the analysis:
- 300 Ah total, at 80% SOC = 240 routinely usable Ah
- 440 Ah @ 50% SOC still = 220 Ah routinely usable

And then there's the cost of 3x Fireflies versus something like the 4x Lifeline 6V AGMs. Probably some weight difference, overall. (Haven't done those comparisons).

And then there's the idea of 6V Fireflies, perhaps sometime in the future:
- 440 Ah @ 80% SOC = 352 routinely usable Ah

-Chris

ranger42c said:

And then there's the idea of 6V Fireflies, perhaps sometime in the future:
- 440 Ah @ 80% SOC = 352 routinely usable Ah

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If I had to guess, I would rationalize the price hike for the Fireflies was due to the inability to meet demand. If they can't meet the demand for 12V batteries, why would they want to venture into the 6V arena any time soon?

ranger42c said:

And then there's the idea of 6V Fireflies, perhaps sometime in the future:
- 440 Ah @ 80% SOC = 352 routinely usable Ah

-Chris

Click to expand...

Chris,

Keep in mind that with many premium AGM batteries, such as Lifeline, Northstar or Odyssey there will usually be no difference in projected cycle life between 6V & 12V. There certainly is when you compare between a cheap garden variety flooded G-24, 27, 31, 4D or 8D batter to a 6V but not so much with AGM..

None of the 12V batteries in the mentioned sizes in flooded are really *"deep cycle" regardless of what the sticker says. (*exception Rolls & Dyno 4D/8D) when compared to the cycle life of a flooded golf cart or L-16 battery. There are also 12V golf cart batteries too, such as a the Trojan T1275, which have equal lab cycle life ratings to their 6V counterparts or double the G24, 27 & 31 cycling ratings..

The cycle life ratings of a premium 12V AGM is usually right in line with the 6V batteries from the same line up.

In other words I don't find that a Lifeline 4CT or 6CT lasts any longer than a Lifeline GPL-31 but I do find that a flooded Group 31 gets easily bested on cycle life when compared to a deep cycle GC battery.

Donsan said:

If I had to guess, I would rationalize the price hike for the Fireflies was due to the inability to meet demand. If they can't meet the demand for 12V batteries, why would they want to venture into the 6V arena any time soon?

Click to expand...

Yep, Bruce said as much (not soon), so I'm not holding my breath...

CMS said:

Keep in mind that with many premium AGM batteries, such as Lifeline, Northstar or Odyssey there will usually be no difference in projected cycle life between 6V & 12V.

The cycle life ratings of a premium 12V AGM is usually right in line with the 6V batteries from the same line up.

In other words I don't find that a Lifeline 4CT or 6CT lasts any longer than a Lifeline GPL-31 but I do find that a flooded Group 31 gets easily bested on cycle life when compared to a deep cycle GC battery.

Click to expand...

Yep, got that. Wasn't thinking about comparing flooded to Firefly, just AGMs like the ones we have now (Odyssey).

Wasn't thinking so much abut long-term cycle life (although important) as I was about immediate Ah gain when I started my whole (almost-) plan about replacing 3XG31s with 4xGCs (probably Lifeline). Not critically necessary, but when we troll on the port engine for 6-8 hours or so, our electronics can bring the starboard bank to its knees.

And then if I do it, I might also add an inverter to that bank... for minor cooking chores (nuke, coffeemaker) and interior stereo and so forth... and I reckon extra available Ah won't hurt for that.

-Chris

CMS said:

When you consider that the other batteries should only be cycled to 50% DOD, in order to maximize cycle life, and they don't handle PSOC use nearly as well, it certainly makes a strong case for these batteries not costing as much as they may appear to, when judged only on the per unit price.

For example: (current street price from my distributors)

Three Firefly G-31's = 330Ah - At 80% DOD = 264 Usable Ah's - $486.00 X 3 = $1458.00

Four Lifeline G-31's = 420Ah - At 50% DOD = 210 Usable Ah's - $370.00 X 4 = $1480.00

Four Odyssey G-31's - 400Ah - At 50% DOD = 200 Usable Ah's - $377.00 X 4 = $1508.00

Four Northstar G-31's - 404Ah - At 50% DOD = 202 Usable Ah's - $390.00 X 4 = $1560.00

Click to expand...

CMS I appreciate you sharing qualified expertise in this extremely interesting battery thread.

In addition to the four comparisons above that you listed do you have a fifth comparison for LA deep cycle batteries. My four in parallel house bank (used to start twin engines too) are East Penn 31's and have provided exemplary performance since 2008. I maintain them well; they are still going strong.

Thanks for input you provide! - Art

CMS

Tossing one back your way. The above assumptions were all based on people drawing their batteries down and especially the advantage of Firefly as it is more conducive to a deeper draw down.

Now, what about the person who doesn't draw the batteries down. Is on either the generator or shore power at all times. What is the advantage, if any, of Firefly to this person?

BandB said:

CMS

Tossing one back your way. The above assumptions were all based on people drawing their batteries down and especially the advantage of Firefly as it is more conducive to a deeper draw down.

Now, what about the person who doesn't draw the batteries down. Is on either the generator or shore power at all times. What is the advantage, if any, of Firefly to this person?

Click to expand...

If I may be so bold as to answer: Nearly Nutten!

Cause... if all you use your boat for is stayen in slip for access to shore power then virtually there taint no big-bad batt-bank necessary! On other hand... if you run gen set 24/7 then little need for a big batt-bank too.

BandB said:

CMS

Tossing one back your way. The above assumptions were all based on people drawing their batteries down and especially the advantage of Firefly as it is more conducive to a deeper draw down.

Now, what about the person who doesn't draw the batteries down. Is on either the generator or shore power at all times. What is the advantage, if any, of Firefly to this person?

Click to expand...

Art said:

If I may be so bold as to answer: Nearly Nutten!

Cause... if all you use your boat for is stayen in slip for access to shore power then virtually there taint no big-bad batt-bank necessary! On other hand... if you run gen set 24/7 then little need for a big batt-bank too.

Click to expand...

Yep, the only advantage I'd see in that situation is the no-maintenance thing... and that's easily acquired with much less expensive AGMs, or Gels, or a watering system on flooded batteries...

MaineSail even has a name for this kind of usage; he calls it UPS-like. (Not the delivery company, not the University...)

-Chris


-Chris

BandB said:

CMS

Tossing one back your way. The above assumptions were all based on people drawing their batteries down and especially the advantage of Firefly as it is more conducive to a deeper draw down.

Now, what about the person who doesn't draw the batteries down. Is on either the generator or shore power at all times. What is the advantage, if any, of Firefly to this person?

Click to expand...

I think you answered your own question..

When batteries are used and hauled around as dead-lead or standby/buffer banks essentially the least expensive battery that will give you the satisfaction, the few times that you actually need them, will suffice.

The Firefly was not designed nor built to be used as a standby/buffer bank battery. It was designed to handle deep cycle PSOC use such as is often seen on cruising boats, especially sailboats, boondocking RV's and off-grid solar. I would not spend the money on any AGM for your described use unless you had a dire fitment issue that excluded flooded batteries.

Art said:

CMS I appreciate you sharing qualified expertise in this extremely interesting battery thread.

In addition to the four comparisons above that you listed do you have a fifth comparison for LA deep cycle batteries. My four in parallel house bank (used to start twin engines too) are East Penn 31's and have provided exemplary performance since 2008. I maintain them well; they are still going strong.

Thanks for input you provide! - Art

Click to expand...

I did not include that because we are not comparing apples to apples.

When a flooded G-31 battery can handle the fast charge rates that AGM batteries do, has the charge efficiencies AGM's do and has the self discharge characteristics etc. then it would be a more apples to apples comparison.

You'll notice that I also did not compare the Firefly to the Deka G-31 AGM either because that is not a true deep cycle AGM product and has rather low lab cycle life (especially compared to the East Penn GEL). It also performs rather poorly in a PSOC application, much, much worse than Lifeline, Northstar, Firefly and Odyssey.

Also the Firefly, Lifeline, Odyssey etc. will all out cycle an EP G-31 flooded battery so if you were to run a cycles to $$ comparison you might be surprised at how expensive an EP G-31 really is when put into a cycling application.. Even East Penn rates that battery at just 350 lab cycles to 50% DOD but in the real world where we tend to abuse batteries those often turn into 65-130 cycle batteries.. The Odyssey & Northstar are rated at 400 cycles to 80% DOD and the Firefly in excess of 1000 cycles to 80% DOD. My beater Firefly has been to 10.5V/0% capacity now approx 36 times and has cycled to 80% DOD no less than 140 times and still delivers 100% of its capacity. Most probably don't find that remarkable, because they have no idea of their batteries actual Ah capacity, but until you test battery capacity as part of your career/job then you'd be shocked to see how batteries compare.

A fairer comparison would be a true deep cycle battery like a GC2, T1275, L-16 etc. etc. but they still don't have the charge efficiency nor the fast charging capability that an AGM has, so of one is looking for that, then a flooded battery is simply out of the mix.

Actual deep-cycle flooded batteries such as golf cart batteries (T105's etc.), T1275's GC12 batteries, J-305's, J-185's, J-150's, L-16's etc. (G24, 27, 31, 4D & 8D are not actually deep cycling batteries other than on the sticker) are much less money and can cycle really well but they don't do what an AGM can in terms of fast charging. Some boaters are looking for this.

If you are not looking for AGM characteristics nothing really beats a true deep cycle flooded battery in value.

Unfortunately your EP G-31's are not really a "deep cycle" battery so the 8 year life is most likely from not PSOC cycling them and keeping them charged most of the time (standby/buffer batteries). Put those batteries into a cycling/PSOC application and they are a 1-4 year, 65-130 +/- cycle battery pretty consistently.

If you are not interested in the premium features of an AGM, then there is nothing wrong with quality deep cycle flooded batteries and they are, and have always been, a tremendous value..

Does the number of expected cycles from a Firefly vary inversely to the DOD like it does with AGMs? Or is the number of cycles regardless of the DOD?

I guess I'm trying to get clear on the advantages. I totally get the advantage of running to a greater DOD, and I get the resulting advantage of spending more of your charging time in bulk rather than absorb. That part is all good. Beyond that, is it

1) More lifetime cycles than an AGM at any given DOD?

2) Lifetime cycle expectancy that is independent of DOD?

3) Complete or just better immunity to sulfation at PSOC?

4) Higher bulk acceptance current than AGMs?

5) Shorter absorb time because it can accept higher currents to a greater SOC than AGMs?

Thanks. This is all very interesting.

twistedtree said:

Does the number of expected cycles from a Firefly vary inversely to the DOD like it does with AGMs?

Click to expand...

Not sure I understand this question to CMS, TT. Far as I know, cycle life of ALL batteries -- any chemistry, like lead acid; any format, like flooded or AGM) -- goes down as cycles at greater DoD goes up.

I think. (And I'm not sure if/how/whether that applies to LiFePO4...)

FWIW, I also think I understand Firefly batteries ARE AGMs, just the "carbon foam" part makes them different from other AGMs.

-Chris

I get about 5yr out of a grp 31 flooded batt in a sub-optimal duty cycle. 100-150bucks. Not worth it to spend much more unless I can be convinced they will last 10-15yrs.

ranger42c said:

Not sure I understand this question to CMS, TT. Far as I know, cycle life of ALL batteries -- any chemistry, like lead acid; any format, like flooded or AGM) -- goes down as cycles at greater DoD goes up.

I think. (And I'm not sure if/how/whether that applies to LiFePO4...)

FWIW, I also think I understand Firefly batteries ARE AGMs, just the "carbon foam" part makes them different from other AGMs.

-Chris

Click to expand...

Yes, that's what I mean. Greater DOD yields fewer cycles. Smaller DOD yields more cycles. If one goes up, the other goes down - that's the inverse relationship I was referring to.

I'm guessing carbon foam behaves the same way, but don't know. What I really am trying to understand in this one regard is whether the relationship between DOD and life cycles is really different for carbon foam. There is no reason you can't take your AGMs down to 80% DOD on a regular basis, but it will yield fewer lifetime cycles. The shallower DOD you cycle to, the more cycles you get. There seems to be a heavy focus on 80% DOD with carbon foam, and I'm trying to understand what's really different, or if they are just shining a light on a well-known (well, apparently not so well known) characteristic of all LA batteries.

Ski in NC said:

I get about 5yr out of a grp 31 flooded batt in a sub-optimal duty cycle. 100-150bucks. Not worth it to spend much more unless I can be convinced they will last 10-15yrs.

Click to expand...

I have not yet tried this myself, but think there is a very strong argument in favor of Ski's approach. Basically run the batteries hard, then replace them. It all comes back to the fact that they can delivery a relatively fixed number of AH over their life. You can consume them in a large number of shallow cycles, or a small number of deep cycles, or anything in between. It's your choice.

The alternate approach is to cut the battery bank in half and double your planned DOD from 40% to 80%. You will get half the number of cycles before needing to replace the batteries, but you will have spent half the money on the batteries in the first place. And in the shorter time you own the batteries, you have 1/2 as much opportunity to trash them in other ways. And by running to 80% DOD, your charger runs more of it's time in bulk mode rather than absorb, so you get that advantage too.

One variable is how hard it is to change batteries on your boat. If it's really hard, this may be less attractive than if it's pretty straight forward. But remember, you will have half the number so it will already be half as hard.

CMS said:

If you are not looking for AGM characteristics nothing really beats a true deep cycle flooded battery in value.

Unfortunately your EP G-31's are not really a "deep cycle" battery so the 8 year life is most likely from not PSOC cycling them and keeping them charged most of the time (standby/buffer batteries). Put those batteries into a cycling/PSOC application and they are a 1-4 year, 65-130 +/- cycle battery pretty consistently.

If you are not interested in the premium features of an AGM, then there is nothing wrong with quality deep cycle flooded batteries and they are, and have always been, a tremendous value..

Click to expand...

Due to our extremely conservative 12 volt batt usage (120v stove/oven, fridge... etc) while anchored aboard boat it is not often that our 4 batt house bank is let to go below 60% charge and then fully recharged by gen set or engine running. We do not use a converter. And, yes... the 8 yr old EP 31 G's are a tremendous dollar value. At $100 a piece when purchased ($400 + tax eight years ago) they are currently costing me an approx. deferred cost of only $50 per year ... which is lessening in annual cost with each passing year of their use.

It is my belief that our house batt problems will eventually be solved by recycling.

The number of coal fired cars that use a huge battery pack is increasing , and those batts all have a limited service life.

The off grid house and car folks are purchasing these old packs , disassembling 3 or 4 of them , selecting the good batts and re assembling.

I do not think it will be long before this is done as a commercial venture and 1000AH sets will be sold or rented.

As these sets are small and powerful we might own a modest house set and rent a big set for a long cruise.

FF said:

The number of coal fired cars that use a huge battery pack is increasing , and those batts all have a limited service life.

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You mean natural gas-fired cars, don't you? Not sure who's service area you're in, but coal only produced 4% of Florida Power and Light's total generation in 2014.

CMS,

How sensitive are firefly batteries to charge voltage? It is easy to cook an AGM should something go bad in the charging system. Wet cell batteries are more resilient. What about fireflies?

Gordon

twistedtree said:

Does the number of expected cycles from a Firefly vary inversely to the DOD like it does with AGMs? Or is the number of cycles regardless of the DOD?

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Number of cycles and how deep always drives a batteries decline. The Firefly has a design cycle life of 1000 cycles to 80% DOD and 3600 cycles to 50%. The carbon foam makes this possible. The carbon foam limits and minimizes the sulfate from hardening and clustering something that murders other batteries when PSOC cycled.

twistedtree said:

1) More lifetime cycles than an AGM at any given DOD?

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Yes because it is sulfation that is almost always the death of marine batteries.

twistedtree said:

2) Lifetime cycle expectancy that is independent of DOD?

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No.

twistedtree said:

3) Complete or just better immunity to sulfation at PSOC?

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Not immune but significantly better. All batteries create lead sulfate upon discharge, the Firefly form sulfation on the plates but unlike other batteries the sulfate left behind in PSOC cycling use is recoverable even after as much as 30+ days of PSOC cycling.

Cycle #1 - This graph is showing at cycle #1 the as new tested Ah capacity using BCI standard testing procedures for 20 hour capacity testing.

Cycle #2 - Takes the battery to 11.7V at the 20 hour discharge rate or about 25% SOC on the Firefly.

Cycle #3 - From cycle #3 through #32 the test used an 11.7V cut off voltage at the 20 hour discharge rate at 77F. The battery was then recharged with a timed 1 hour 50.6A current or .46C charge rate. You can see the PSOC cycling capacity "walk down" as sulfate forming on the plates shortens how much energy can be put back into the battery in the 1 hour duration at 50.6A.

Essentially as the PSOC cycling goes on the battery attains absorption voltage earlier in the hour, and less energy can be stored in the plates as can be seen by the walking down of "usable PSOC capacity".. You may also notice some "ping pong" effect where one cycle is a lower capacity and the next slightly higher. This is due to the slightly longer times spent at absorption voltage in the previous cycle and recovering some more of that sulfation. At cycle #3 the charger never exited bulk and 49.7Ah's out of a 50.6A charge rate was fully usable back down to 11.7V. This means a very high bulk charge efficiency.

Cycle #33 - This cycle followed a 1 hour .46C recharge but the battery was taken to 0% SOC or 10.5V (BCI bottom voltage for 20 hour test)..

Line #34 - Initial capacity test after 30 PSOC cycles to 80% DOD. This is where I thought I had the Firefly beat, but I spoke with the Firefly inventor and he told me to discharge to 10.5V once more and do another full recharge. I doubted it seeing as the battery was only at 94Ah's a loss of 16Ah's of capacity.

Line #35 - On the second capacity test the battery recovered all of it capacity with no capacity loss at all. To this day after much more of a beating that battery still has all its capacity. No other AGM battery survived this testing with all its capacity and one AGM lost 30% of its capacity or 1% per day when PSOC cycled.

twistedtree said:

4) Higher bulk acceptance current than AGMs?

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Comparable to other AGM's but the thin plate batteries (TPPL's) sometimes hold bulk an SOC percent or two longer.

twistedtree said:

5) Shorter absorb time because it can accept higher currents to a greater SOC than AGMs?

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Again comparelbe to other AGM's. The secret to the Firefly is in sulfation resistance and net cycle life.. It would have shorter absorption times than flooded because an AGM battery requires less over charging to attain 100% SOC than flooded batteries do. At .4C I can take a Lifeline to 95% SOC, from 50% SOC in just two hours even though it hit absorption at 19 minutes. The last 4%, which is critical for longevity, takes 3.5 hours. With the Firefly you can stay out of this slow charging range for longer in-between times.. AGM's in general attain and hold higher currents for longer than flooded batteries will.

Simple math with the Firefly shows that it hits absorption at approx 70-71% SOC when charged at .46C. A .46C charge rate is a massive charge rate. A 440Ah bank would need to be charged at 202A to mimic this on a boat.

The bulk to absorption point at SOC% is driven by the charge rate applied to the battery. A higher charge rate means longer times spent in absorption, if pushing above the absorption point. Early absorption is still fairly efficient but the longer you stay in absorb the less efficient it becomes. A lower charge rate means longer times in bulk. Most boats will not even have .25C to .3C in charge capability so the Firefly, or any AGM, would will stay in bulk to a higher SOC..

The benefit to the Firefly is its ability to deal with abusive PSOC use and come back to live another day. If you don't PSOC cycle your batteries then the benefit and greatest feature of the Firefly would not be taken advantage of. Batteries need to be chosen to match use and all AGM's, & GEL too, should be installed using a "system-approach" not just as a drop-in for flooded batteries, if you want to maximize your dollar spent..

Gordon J said:

CMS,

How sensitive are firefly batteries to charge voltage? It is easy to cook an AGM should something go bad in the charging system. Wet cell batteries are more resilient. What about fireflies?

Gordon

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If you don't have temp compensation for all charge sources, can set absorption to 14.4V and float to 13.2V (float at 13.2V is very important) then I would not suggest buying Firefly batteries.