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Old 23-09-2016, 06:03   #31
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Re: Firefly Oasis Carbon Foam AGM Batteries

[QUOTE=Sternwake;2219203]
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Originally Posted by Journeyman View Post
Sternwake,

Thanks for this input. Can you quantify what "easily notice changes in my NorthStar battery after a few PSOC cycles means"?/QUOTE]


I typed a longer reply but it disappeared due to the time it took. Cursing ensued. Here is the short version.

I watch my battery monitor closely over nearly each discharge cycle.

Voltage held Under X amount of load for X amount of AH removed.

Without the high amp recharge, voltage held under the load for the same AH removed gets lower and lower, until it gets this high amp recharge.

The high amp recharge not only returns voltage to the high end of my expectations during house battery usage, it also cranks my engine faster.

Simply holding absorption voltage for long enough is not enough to keep my battery happy in deep cycle usage, the high amperage recharge is Key, and my plug in source can manage ~0.45c, my solar can manage 0.1c, and my alternator can achieve 1C, if only briefly.

Better click send before I get denied again and want to throw things into low earth orbit
That's very interesting to hear. High charge acceptance rate AGM battery specs do require high charge rates, so the implication is that slow recharge rates are not a good thing. Your experience seems to confirm that. Off hand, you'd think that how LONG it takes to reach specified Float conditions would not be a factor. That is, a fully charged battery is a fully charged battery. But it seems the electrochemistry of charging says that lots of current in a short period of time breaks up the sulphate crystal residue on the negative plates more thoroughly, allowing for more stored charge before Float parameters are met.

We observe that our shore charger (100A nominal) bringing the batteries up from from 50% to full, seems to stay in Absorption much longer than when alternator recharging. This despite both the shore charger and the alternator voltage regulators being programmed to 14.7V Absorption and 13.6V Float.

This would seem to argue well for high current engine charging versus low current solar charging?
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Old 23-09-2016, 08:52   #32
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Maggiedrum,
Thanks for that very informative summary of your experience.

Very much agree we have different cruising objectives. We would never spend 3-4 weeks in one anchorage.

We commuter cruise and really enjoy being based in nice marinas and the local cruising grounds surrounding them typically within a couple hundred mile radius. There’s a reason nice marinas are located where they are. We also enjoy the longer sails when its time to stage the boat in new cruising grounds, and find our simple charging discipline offshore scales well.

We would never try and use the engine just to reach 100% SOC battery charge. That comes free as a consequence of the inevitable motoring incurred within the 7-10 day window mentioned above.

Totally agree about AGM abuse leading to unhappy boaters. But again you cannot blame a product or technology that is asked to do something it was not designed to do.

An electric system on a boat needs a mindset and a discipline. Read the manufacturers instructions on use (not the marketing brochure – the owners manual) and do not deviate. I think its sad that many boaters interpret a “better battery” or “better alternator” or “better voltage regulator” as a way to improve their electrical system without understanding its real context in the system. Unfortunately, this perception makes money for businesses regardless of the end result.

You mention that “If the Fireflys can live with a PSOC for their lifetimes, then that would be a major advance in regards to the charging requirements as the power (and power over time) to recharge them to 80% is much less”. Can you send me a link to that claim? When we researched FireFly there was a shocking absence of any characterization data on them. Not even charge acceptance rate data. Compare that to the volume of test results from Enersys. For example, if power-in to recharge them is “much less” than comparable advanced AGMs, it should make for an amazing read. I just went to their site, and there is still nothing there except the “case study” in Practical Sailor that when read carefully simply states that if you compare a grossly abused AGM battery with a FireFly, the FireFly will do better.

MaineSail
I know you don’t mean to, but in the above post you seem to imply PSOC “walk down” as the same as permanent PSOC incurred damage. As you know, observing the discipline of 7-10 day full recharges self corrects this temporal condition to a degree that it becomes unnoticeable in practical usage - which you state elsewhere in the same post.

Obviously I am keenly interested in marine electrical power systems, not trying to knock any product, just trying to follow the facts. Cheers, J
Hi J,

It appears we are in violent agreement about most all of this. My "hope" was that the Fireflys would not require a constant recharge to 100% to maintain a long life cycle. This was indeed a hope and not something I really know happens. They don't seem to be the panacea to all the issues AGMs have now.

I continue to recommend AGMs for the boaters with the appropriate cruising style and charging opportunities. I would keep mine if my plans agreed more. For instance, if I did not plan on going offshore and to hot climates where even short engine runs times are an issue. Hot engines are a drawback to even short hops to different anchorages on a frequent basis but, alas, that's one thing you do for the lifestyle.

I am going to "donate" my AGMs to a powerboater friend as soon as I determine his charging system can handle AGM charge profiles. If he can't they'll have to go somewhere more appropriate.

Cheers,
Joe
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Old 23-09-2016, 09:33   #33
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Re: Firefly Oasis Carbon Foam AGM Batteries

@exMaggieDrum:

I can't understand the data you posted. There must have been something completely wrong with your solar setup if 400Wp of solar can't get the last 5% into a 440Ah bank. Or you are using extremely much energy even while anchored at daylight.

We've got 280Wp and a 220Ah AGM bank that is very often charged up to 100% only by solar by midday. If there are two very cloudy days in a row, we have to run the engine for an hour in the second morning but even then the solar array is charging at about 5 Amps when the engine is stopped at about 90% and gets the bank up to 100% by early afternoon.

What i sometimes do is turn the fridge to full power and charge all our laptops, phones etc. as long as the engine is running. Then the boat will use nearly zero power for some hours after the engine is turned off and the solar array can charge our battery bank without any problems.
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Old 23-09-2016, 09:39   #34
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Originally Posted by txg View Post
@exMaggieDrum:

I can't understand the data you posted. There must have been something completely wrong with your solar setup if 400Wp of solar can't get the last 5% into a 440Ah bank. Or you are using extremely much energy even while anchored at daylight.

We've got 280Wp and a 220Ah AGM bank that is very often charged up to 100% only by solar by midday. If there are two very cloudy days in a row, we have to run the engine for an hour in the second morning but even then the solar array is charging at about 5 Amps when the engine is stopped at about 90% and gets the bank up to 100% by early afternoon.

What i sometimes do is turn the fridge to full power and charge all our laptops, phones etc. as long as the engine is running. Then the boat will use nearly zero power for some hours after the engine is turned off and the solar array can charge our battery bank without any problems.
Your energy usage was different than mine I guess. We did not turn off everything to just allow the batteries to charge 100% with solar. We often had to run our Honda generator at anchor to make up for the difference. I make no apologies for our usage patterns. They were what they were. They were not that much different than that of many cruisers that I know have in Mexico right this moment.

I can see how you could do so if you did not have to run anything else. BTW - we did not have the necessity to be charging all of our laptops, cellphones, etc. as we did not use them that much - 10 years ago. Wifi was almost non-existent at the Mexican anchorages then. So I guess we had even less excuse to use power. But we did have refrigeration and other things.
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Old 23-09-2016, 09:47   #35
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Re: Firefly Oasis Carbon Foam AGM Batteries

While at anchor most of our energy usage is in the evening with lights (we do have ac lighting running through an inverter) and often two laptops.

During the day at anchor there is nearly nothing except the fridge which probably uses about 1-2 Amps on average.

So that's why i've asked if you had a lot of equipment running. When 400 Watts of solar can't charge the last 5% of a 440Ah bank, there must be some serious current draw. E.g. two or more rather inefficient fridges or onboard computers running all the time. Either that or there was something wrong with your solar setup.

With our 280Wp array (two 140Wp panels with independet MPPT Controllers) we're seeing up to 17 Amps charge current, and on average it is probably 10-12 Amps.
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Old 23-09-2016, 10:24   #36
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Re: Firefly Oasis Carbon Foam AGM Batteries

regarding use of FF batteries . this from memory so don't jump down my throat . the batteries walk down the same as Agm s doe bur they can recover by giving them a full discharge (10.5 volts I think) and then a full recharge . I plan to do this in Dec. when I return to the boat. Once again the point being that they can recover from incorrect but typical use .
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Old 23-09-2016, 11:23   #37
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Originally Posted by Journeyman View Post
MaineSail
I know you don’t mean to, but in the above post you seem to imply PSOC “walk down” as the same as permanent PSOC incurred damage. As you know, observing the discipline of 7-10 day full recharges self corrects this temporal condition to a degree that it becomes unnoticeable in practical usage - which you state elsewhere in the same post.

Obviously I am keenly interested in marine electrical power systems, not trying to knock any product, just trying to follow the facts. Cheers, J
PSOC walk down is what occurs during cycles when you do not return the battery to 100% SOC and then discharge it again. Walk down begins occurring as fast at 1-2 cycles off a full charge. This is a "walk-down of your usable stored capacity during PSOC cycling. Even with the same DOD & charge rate and charge duration the next cycle nets less usable capacity or less energy stored in the plates of the battery.. This is what is known as PSOC capacity walk down.

PSOC walk down does not mean this capacity loss is permanent, just that sulfate has formed and is not allowing the same amount of "usable" energy to be stored in the battery at the same charge rate and duration as the cycle before. This is observed in all lead acid batteries including the Firefly. If batteries are charged to full often enough this can be self corrective, but not always, and not for all brands.

Permanent damage occurs from PSOC cycling and the duration of PSOC use, between full recharges, that cause permanent damage, varies from battery to battery.

There is no scientific data I know of that suggests that every 7-10 days is optimal or is completely self corrective for all AGM's. Every seven to ten days is sub optimal for many batteries and their permanent capacity loss can be surprisingly fast. Some batteries can go slightly longer and some slightly less between 100% SOC events but "optimal" as defined by almost all AGM makers is "Return to full after each discharge"...

The Practical sailor test ran 30 PSOC cycles to 80% DOD and used a recharge rate of .46C for exactly 1 hour. This DOD level and charge duration is not out of the ordinary use for many sailors. In a Battery Use Survey conducted by Sailboatowners.com 64.3% of responders answered that they did not consider recharging until below 11.9V with 46.7% of those 64.3% answered 11.7V or less. We had 1043 sailors & trawler owners answer that question.

Discharging to 80% DOD is also advised use for Firefly and marketed use for Odyssey and Northstar. Lifeline used to market their AGM's for 80% DOD as did East Penn early on. Any battery described as deep-cycle should be designed to be cycled to 80% DOD. Some do this well and some fail miserably at it. For "optimal" cycle life most, except Firefly, suggest 50% max regular DOD despite "marketing" them for 80% DOD..

Because the bulk stage is a significantly more efficient stage of charging, upwards of 98% of the Ah's delivered to the battery in bulk is able to be pulled back out on the next cycle, the system use becomes more efficient too. The ability to cycle to 80% DOD can yield some tremendous benefits in terms of storing more usable energy from short duration engine runs.

For example in the first PSOC cycle to 80% DOD, before the Lifeline AGM began walking down, a .46C charge rate for 1 solid hour never even attained 14.4V/absorption and of the 48.3 Ah's that were sent to the battery the next cycled delivered 46.56Ah's taken back out. This is an in/out efficiency of 96.4%.. Contrast that to a Lifeline battery discharged to 50% SOC and then recharged at .4C, a lower charge rate, and that battery hit 14.4V at just 19 minutes. This means your expensive alternator is only being use efficiently for 19 minutes with a .4C charge rate from 50% SOC.. Once the battery hit 14.4V it became voltage limited and charging speed dramatically dropped off. Sadly for most lead acid batteries taking them to 80% DO regularly really spells a quick death. The ability to go to 80% DOD goes greatly under appreciated and certainly does not get the "press" it deserves.

Only one other battery in the PS test was marketed as a PSOC resistant battery and it certainly bested the East Penn and Lifeline battery, and was on-par with Odyssey, but it did not handle the abuse the Firefly did.

I am not a believer that a general number of 7-10 days can be applied to all batteries for PSOC use recharge.. Some will need more frequent 100% recharges and some, like the Firefly, can go even longer between 100% SOC events.
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Old 23-09-2016, 11:35   #38
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Re: Firefly Oasis Carbon Foam AGM Batteries

Also for others that think they are returning their AGM batteries to fully, 100% charge with Solar alone, regardless of how much Solar they have, I have it on good authority, your not.
Reason has nothing to do with how much Solar you have, it has to do with battery acceptance rate and number of useable Solar hours there are on an average day. It just simply takes longer to fully recharge your bank than your Solar is supplying useable current.
It was this revelation that finally decided me that I would have to have a generator, cause I want to return my bank to 100% twice a week, this also aligns with how often I plan on making water and washing clothes etc. and would be running a generator anyway.



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Old 23-09-2016, 11:40   #39
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Originally Posted by Journeyman View Post

That's very interesting to hear. High charge acceptance rate AGM battery specs do require high charge rates, so the implication is that slow recharge rates are not a good thing.
This is very repeatable in my usage. My Northstar appears to crave the high amp recharge, and I love that it has no fear of it. My experience indicates it needs to be applied when battery is lowest and in the 50% charge or less arena. if the solar has a few hours to work, and then I plug in and apply that 0.45c rate, obviously absorption voltage is reached faster, and it takes less amperage to reach it, and it does not appear to be as effective as if I applied a 0.45C rate before the sun rose.

Someone smarter than me said the high amperage forced electrolyte migration through and around the plates. Perhaps the higher temps incurred at higher amp rates also help to dissolve sulfation.

I wonder about minimum charge rates of the Firefly, whether the low and slow to full is OK or if the higher amp rates are occassionally required.

Also wonder about the possible leaking of electrolyte from the vents on the initial 60 cycles. I've read one report of this in Rv usage and about replacement vents fixing the issue.

Can Firefly be used on their sides?
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Old 23-09-2016, 11:41   #40
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Originally Posted by a64pilot View Post
Also for others that think they are returning their AGM batteries to fully, 100% charge with Solar alone, regardless of how much Solar they have, I have it on good authority, your not.
Reason has nothing to do with how much Solar you have, it has to do with battery acceptance rate and number of useable Solar hours there are on an average day. It just simply takes longer to fully recharge your bank than your Solar is supplying useable current.
My Victron battery monitor tells a different story. Charge current drops to 1-2Amps at 14,4V for a 220Ah AGM bank which means full.

Both voltage and current measurements of the monitor are checked against a calibrated multimeter and are correct.
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Old 23-09-2016, 11:52   #41
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Re: Firefly Oasis Carbon Foam AGM Batteries

ANyone know if these Outback nano-carbon batteries are similar to the Firefly construction?
Quote:
Outback Power Batteries launched the new EnergyCell Nano-Carbon with the advanced PSoC technology that will allow extended life of a battery in self-consumption applications.The Nano-Carbon is an enhanced and optimized negative active material formulation which makes it more than just a carbon additive but improves charge efficiency and allows PSoC operation with improved deep discharge recovery.
https://www.emarineinc.com/categorie...ower-Batteries
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Old 23-09-2016, 12:05   #42
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Re: Firefly Oasis Carbon Foam AGM Batteries

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My Victron battery monitor tells a different story. Charge current drops to 1-2Amps at 14,4V for a 220Ah AGM bank which means full.
If using return amps for defining 100% the ranges for a full AGM vary from about 0.3% of Ah capacity at absorption to 0.5% of Ah capacity at absorption voltage.

East Penn
Odyssey
Northstar
0.3% at absorption voltage is 100% SOC (100Ah battery = 0.3A at 14.4V - 14.7V)

Lifeline
0.5% at absorption voltage (100Ah battery = 0.5A at 14.4V)
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Old 23-09-2016, 12:13   #43
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Re: Firefly Oasis Carbon Foam AGM Batteries

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ANyone know if these Outback nano-carbon batteries are similar to the Firefly construction?

https://www.emarineinc.com/categorie...ower-Batteries

They are not the same.. Firefly owns the patent for Carbon Foam and no one else can construct a battery like it at this point in time.. Those Outback batteries are made by C&D Technologies and use a similar carbon additive to what Trojan's new Reliant & Northstar's Blue+ are now using. In the PS PSOC testing the Northstar TPPL Blue+ with carbon really did not do much, if any better, than the Odyssey TPPL without it. C&D makes a very good telecom product but their use in the marine market is very small as of yet...
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Old 23-09-2016, 16:47   #44
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Re: Firefly Oasis Carbon Foam AGM Batteries

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Here is Nigel's follow up to that:

"After discharging the 24v series/parallel Firefly pack to 38% SoC last August I left the batteries disconnected all winter over (over 8 months). When I got here I did a normal recharge with the 4 batteries in 24v series/parallel mode. I held the absorption voltage overnight (i.e. no specialized voltage/current; just an extended timer on the absorption for a mild overcharge without equalization voltages), ran the batteries in boat use for several hours with a float charge, then did a C20 capacity test. I got right at 110 Ah per block at the C20 rate, so this looks really good. I recharged with a voltage limit of 28.8v (14.4v/block) and a current limit of 0.25C. The 4 batteries maintained an amazingly consistent voltage on discharge and recharge. All-in-all, this is very positive. Nigel"

I think most of us know what 38% SOC for 8 months does to most lead acid batteries, they turn into scrap lead.....
Mainesail,

Odyssey lead acid batteries have similar tested results. And I can attest to an accidental flattening of my bank that showed around 8V after I arrived at the boat after being gone for several weeks. They also recovered, and months later a C20 test showed capacity above 90% on these 6 year old batteries. But I am not sure what these kind of anecdotal or even controlled tests really mean in regard to more important performance characteristics that you need in practical use....

From the Sept 2016 Odyssey Technical Manual:
"(C) Can the battery recover from deep discharge conditions?
Yes, the ODYSSEY battery can recover from extremely deep
discharges as the following test results demonstrate.
(1) German DIN standard test for overdischarge recovery
In this test, a PC925 was discharged over 20 hours (0.05C10
rate)to 10.20V. After the discharge a 5Ω resistor was
placed across the battery terminals and the battery kept in
storage for 28 days.
At the end of the storage period, the battery was charged
at 13.5V for only 48 hours. A second 0.05C10 discharge
yielded 97% of rated capacity, indicating that a low rate
48-hour charge after such a deep discharge was insufficient;
however, the intent of the test is to determine if the battery
is recoverable from extremely deep discharges using only
a standby float charger. A standard automotive charger at
14.4V would have allowed the battery to recover greater
than 97% of its capacity.
These test results prove that ODYSSEY batteries can
recover from deep discharge conditions. Reinforcing this
conclusion is the next test, which is even harsher than the
DIN standard test, because in this test the battery was
stored in was stored in a discharged state at a temperature of 122°F
(50°C)."
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Old 23-09-2016, 17:07   #45
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Re: Firefly Oasis Carbon Foam AGM Batteries

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PSOC walk down is what occurs during cycles when you do not return the battery to 100% SOC and then discharge it again. Walk down begins occurring as fast at 1-2 cycles off a full charge. This is a "walk-down of your usable stored capacity during PSOC cycling. Even with the same DOD & charge rate and charge duration the next cycle nets less usable capacity or less energy stored in the plates of the battery.. This is what is known as PSOC capacity walk down.

PSOC walk down does not mean this capacity loss is permanent, just that sulfate has formed and is not allowing the same amount of "usable" energy to be stored in the battery at the same charge rate and duration as the cycle before. This is observed in all lead acid batteries including the Firefly. If batteries are charged to full often enough this can be self corrective, but not always, and not for all brands.

Permanent damage occurs from PSOC cycling and the duration of PSOC use, between full recharges, that cause permanent damage, varies from battery to battery.

There is no scientific data I know of that suggests that every 7-10 days is optimal or is completely self corrective for all AGM's. Every seven to ten days is sub optimal for many batteries and their permanent capacity loss can be surprisingly fast. Some batteries can go slightly longer and some slightly less between 100% SOC events but "optimal" as defined by almost all AGM makers is "Return to full after each discharge"...

The Practical sailor test ran 30 PSOC cycles to 80% DOD and used a recharge rate of .46C for exactly 1 hour. This DOD level and charge duration is not out of the ordinary use for many sailors. In a Battery Use Survey conducted by Sailboatowners.com 64.3% of responders answered that they did not consider recharging until below 11.9V with 46.7% of those 64.3% answered 11.7V or less. We had 1043 sailors & trawler owners answer that question.

Discharging to 80% DOD is also advised use for Firefly and marketed use for Odyssey and Northstar. Lifeline used to market their AGM's for 80% DOD as did East Penn early on. Any battery described as deep-cycle should be designed to be cycled to 80% DOD. Some do this well and some fail miserably at it. For "optimal" cycle life most, except Firefly, suggest 50% max regular DOD despite "marketing" them for 80% DOD..

Because the bulk stage is a significantly more efficient stage of charging, upwards of 98% of the Ah's delivered to the battery in bulk is able to be pulled back out on the next cycle, the system use becomes more efficient too. The ability to cycle to 80% DOD can yield some tremendous benefits in terms of storing more usable energy from short duration engine runs.

For example in the first PSOC cycle to 80% DOD, before the Lifeline AGM began walking down, a .46C charge rate for 1 solid hour never even attained 14.4V/absorption and of the 48.3 Ah's that were sent to the battery the next cycled delivered 46.56Ah's taken back out. This is an in/out efficiency of 96.4%.. Contrast that to a Lifeline battery discharged to 50% SOC and then recharged at .4C, a lower charge rate, and that battery hit 14.4V at just 19 minutes. This means your expensive alternator is only being use efficiently for 19 minutes with a .4C charge rate from 50% SOC.. Once the battery hit 14.4V it became voltage limited and charging speed dramatically dropped off. Sadly for most lead acid batteries taking them to 80% DO regularly really spells a quick death. The ability to go to 80% DOD goes greatly under appreciated and certainly does not get the "press" it deserves.

Only one other battery in the PS test was marketed as a PSOC resistant battery and it certainly bested the East Penn and Lifeline battery, and was on-par with Odyssey, but it did not handle the abuse the Firefly did.

I am not a believer that a general number of 7-10 days can be applied to all batteries for PSOC use recharge.. Some will need more frequent 100% recharges and some, like the Firefly, can go even longer between 100% SOC events.
Mainesail
I didn’t say all AGMs. I said my AGMs. Think Enersys Odyssey/NorthStar TPPL.
Also never said 7-10 days was “optimal”. Nothing is optimal with batteries other than perhaps never using them
Their Chief Technology Officer gave me the 7-10 day rule of thumb for reasonable recharge maximums.
Also as I said before, marketing giveth and owner’s manual taketh away: TPPL claims at Enersys are that you can get 400 cycles to 80% DOD between recharges. And they define recharge as a full recharge to 105%. I am sure that gets misinterpreted by owners often to just mean “charging up”. Nevertheless, Odyssey is covered by that statement and I am sure they can prove it in the lab. Of course just like the Practical Sailor lab tests, real world results may vary. Elsewhere in their documentation they imply best practices are not to exceed 50% DOD. But I think the real point here is that you can operate a TPPL battery to 80% DOD just as you can with a FireFly, but it will be at the expense of longevity, no? The only difference I see here is that TPPL has been out there for decades and FireFly is new… so to be fair the FireFly verdict is still out and will be for some time on whether their “designed to work at 80% DOD%” claim is just marketing.
An essential requirement from the TPPL owners manual is: “In order to achieve the full design cycle life of ODYSSEY batteries in cyclic applications the charge current must be a minimum of 40% of the battery’s 10-hour rating (column 8 of the chart on page 7)”. They actually say that in BOLD FONT.

Our boat follows these requirements fairly closely and I think that’s why we are pleased with the batteries.

What’s keeping me from buying FireFly is they have no characterization data whatsoever that I can find. The first thing I would like to see is some charge acceptance rate characterization. What size FireFly battery bank would you need to accept a steady 250A (12V) of alternator charging current for one hour from a 50% SOC? Our application predicates on this. The second thing is if as you say there is no PSOC capacity walk-down improvement over AGMs between full recharges, then what is their merit? If its that they are better at recovering from extreme periods of PSOC abuse, then what is required to revive them, and how much longer than the 7-10 days TPPL limit can they go? But then that leads to the question that if they are able to walk-down for many days longer, with ever diminishing capacity, then what is the real value of a higher number of PSOC cycles between full recharges?

My only point in all of this is to encourage a potential buyer to very closely read the claims and characterization data very closely before deciding a product has merit in their application. If you think you cannot install/operate within the guidelines, stay away.

As an aside, I think there is probably a linear correlation between AGM battery fails and the increasing adoption of solar charging over recent years. If AGM battery health seems to be contingent on high inrush current from lower DODs, trying to keep them charged with respect to good longevity using solar seems to be a losing proposition. Furthermore, a battery is undercharged without an appropriate amount of time at Absorption. So if a solar panel takes a TPPL battery up to its Absorption voltage of say 14.7V in the case of TPPL AGM … you are still not charged without several hours at that Absorption voltage. Or in the case of at least one AGM 0.001C10. When solar users say the batteries are “full” or “topped off” do they really mean Absorption is complete, or do they mean “hey, battery voltage is reading 12.9V (or 13V or 14.7V) so we must be fully charged”.
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