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Firefly Oasis carbon foam AGM battery
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shade
Well-known member
I have one on order, with delivery expected in January. It's a new model that fills a gap in Victron's product line. There aren't many products that offer that level of control of DC-DC charging.
30A should be fine for my uses with an LFP battery, but multiples can be run if more charge current is desired.
It really does look awesome, I would be very interested to hear details of your install and experience.
Back on topic ...
ok so lets assume sulfation was the cause of the battery failure (measured capacity ~75%)
After a few EQ attempts (following FF recommended parameters with normal cycling in between) capacity is now below 60% (resting OCV is still above 12.9V)
Clearly there is debate with respect to the effectiveness of an EQ charge as a restorative measure for AGM capacity. However, FF support also recommended periodic EQ charging as a preventative measure when operating at psoc. I suppose one could question the relevance of testing EQ effectiveness on a failed battery, but it seemed like a good use prior to recycling and some data being better than no data.
I would have interpreted no change in capacity as evidence that EQ is ineffective at reversing sulfation build up. The loss of capacity seems to suggest the battery is critically sensitive to gassing. Minimizing gassing is recommended given the long life of the battery ... but in my observation just 4-5 hours of EQ resulted in a measurable decrease in capacity (~5Ah). This is what lead me to wonder if sulfation was actually the cause of the initial failure of the battery. If the actual cause was AGM dry out it would seem logical that any additional time gassing would further reduce capacity (electrolyte limited capacity, vs sulfate electrode surface limited capacity), rather than just reducing life expectancy some time down the road after years of service.
The FF charging recommendations published 07.11.16 (worth noting this document is not available on the FF website) state that charging should be discontinued once current drops to 3.3A for a G31 which would seem to be a tip-off to overcharge sensitivity. Where as FF support states that charging should be continued until 0.5-0.6A to reach full capacity.
So unfortunately I don’t have any concrete conclusions to share. Perhaps my observations may be of use so someone particularly around EQ.
Re-reading the 07.11.16 charging recommendations I noted that operation between 10%-90% soc is recommended for long life and full charge is recommended every 20-30 days.
Charging whenever possible as John recommends would appear to be sound advice with no downside, although I wonder which cutoff should be used 3A or 0.5A
I would really like to see FF publish a manual that covers charging in depth.
Back on topic ...
ok so lets assume sulfation was the cause of the battery failure (measured capacity ~75%)
After a few EQ attempts (following FF recommended parameters with normal cycling in between) capacity is now below 60% (resting OCV is still above 12.9V)
Clearly there is debate with respect to the effectiveness of an EQ charge as a restorative measure for AGM capacity. However, FF support also recommended periodic EQ charging as a preventative measure when operating at psoc. I suppose one could question the relevance of testing EQ effectiveness on a failed battery, but it seemed like a good use prior to recycling and some data being better than no data.
I would have interpreted no change in capacity as evidence that EQ is ineffective at reversing sulfation build up. The loss of capacity seems to suggest the battery is critically sensitive to gassing. Minimizing gassing is recommended given the long life of the battery ... but in my observation just 4-5 hours of EQ resulted in a measurable decrease in capacity (~5Ah). This is what lead me to wonder if sulfation was actually the cause of the initial failure of the battery. If the actual cause was AGM dry out it would seem logical that any additional time gassing would further reduce capacity (electrolyte limited capacity, vs sulfate electrode surface limited capacity), rather than just reducing life expectancy some time down the road after years of service.
The FF charging recommendations published 07.11.16 (worth noting this document is not available on the FF website) state that charging should be discontinued once current drops to 3.3A for a G31 which would seem to be a tip-off to overcharge sensitivity. Where as FF support states that charging should be continued until 0.5-0.6A to reach full capacity.
So unfortunately I don’t have any concrete conclusions to share. Perhaps my observations may be of use so someone particularly around EQ.
Re-reading the 07.11.16 charging recommendations I noted that operation between 10%-90% soc is recommended for long life and full charge is recommended every 20-30 days.
Charging whenever possible as John recommends would appear to be sound advice with no downside, although I wonder which cutoff should be used 3A or 0.5A
I would really like to see FF publish a manual that covers charging in depth.
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shade
Well-known member
That would be a good follow-up question for Firefly. It may be that they need to update their 2016 guidance.
luthj
Engineer In Residence
Lead acid has something called the shuttle reaction, which makes them resistance to "overcharging". Typically the only major concern is high voltages, usually over 14.6V. This can cause hydrogen/oxygen to build up faster than the catalyst can convert it, resulting in venting of the battery through the safety valve.
Obviously extending float at high voltages isn't good either.
Obviously extending float at high voltages isn't good either.
DaveInDenver
Middle Income Semi-Redneck
What is that? I've heard of a "redox shuttle additives" in reference to overcharge protection for lithium-ion. Just haven't heard of it w.r.t. to lead-acid. Have you got a primer you could point to?
luthj
Engineer In Residence
I can't seem to find my reference materials currently (might be on my other computer). From memory, Lead acid has a naturally occurring species of lead (oxide II?) which oxidizes on the cathode, and then diffuses back to the anode. This occurs as part of a continuous cycle above a certain cell voltage. This process converts some of the charge energy into heat, and prevents oxidation of of the cathode at full charge potential/voltage. In addition you have electrolysis of the electrolyte, which can occur reversibly in the background at high voltages (except for gel batteries where the gas formation is deleterious.
At least that's my recollection of the details.
The FF "capacity restore" cycling should not be called an equalization protocol, and is not itself harmful.
FF do **not** get equalized, as with all other quality AGM except for Lifeline.
However what both procedures have in common is that they are primarily a tool to be regularly if not frequently used for **prevention** of permanent capacity loss.
If you think of them as "resuscitating" damaged batteries, the permanent damage has been done and best you can do is limp along for a tiny fraction of what their cycle lifespan would have been if cared for properly all along.
For FF specifically, the PSOC cycling periods should ideally be rare and short, and the CR procedure executed regularly. If PSOC abuse is chronic, the rule rather than the exception, **and** CR run rarely, then lifespan will be greatly reduced.
Not **as** drastically as any other lead formulation - that is FF's unique value proposition - but still.
wrt endAmps, the original spec Bruce gave me for the G31 was 1.5A, and that's what I will continue to recommend for "normal cycling whenever possible", unless corrected.
However, depending on the context, I do not see any harm in pushing Absorb/CV further, even to 0.5A, **especially** if it's only possible to get there say once or twice a week.
Conversely, if a given setup can get there **every single cycle**, say sitting at shore power, I also see no harm in stopping a little earlier at say 3A.
All of these are just slight variations of a "full charge", and **that** term should also not be used for the full "capacity restore" cycling procedure.
There is **no way** that more frequent PSOC cycling is "healthier" than getting to Full, doing that more frequently is **always** better, and reduces the need/frequency for the CR routine.
And **no way** frequent 90% DoD is ever "healthy"; again, it's just that the longevity curve is **much less** affected than any other lead.
Shallower deep cycling **always** means more lifetime cycles, no exceptions just as true for lithium as well BTW.
FF do **not** get equalized, as with all other quality AGM except for Lifeline.
However what both procedures have in common is that they are primarily a tool to be regularly if not frequently used for **prevention** of permanent capacity loss.
If you think of them as "resuscitating" damaged batteries, the permanent damage has been done and best you can do is limp along for a tiny fraction of what their cycle lifespan would have been if cared for properly all along.
For FF specifically, the PSOC cycling periods should ideally be rare and short, and the CR procedure executed regularly. If PSOC abuse is chronic, the rule rather than the exception, **and** CR run rarely, then lifespan will be greatly reduced.
Not **as** drastically as any other lead formulation - that is FF's unique value proposition - but still.
wrt endAmps, the original spec Bruce gave me for the G31 was 1.5A, and that's what I will continue to recommend for "normal cycling whenever possible", unless corrected.
However, depending on the context, I do not see any harm in pushing Absorb/CV further, even to 0.5A, **especially** if it's only possible to get there say once or twice a week.
Conversely, if a given setup can get there **every single cycle**, say sitting at shore power, I also see no harm in stopping a little earlier at say 3A.
All of these are just slight variations of a "full charge", and **that** term should also not be used for the full "capacity restore" cycling procedure.
There is **no way** that more frequent PSOC cycling is "healthier" than getting to Full, doing that more frequently is **always** better, and reduces the need/frequency for the CR routine.
And **no way** frequent 90% DoD is ever "healthy"; again, it's just that the longevity curve is **much less** affected than any other lead.
Shallower deep cycling **always** means more lifetime cycles, no exceptions just as true for lithium as well BTW.
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No, that is true for FLA, but only long as you keep water topped up.
But VRLA will lose electrolyte from "AHT too long" overcharging even with voltage held within spec, and that definitely shortens lifespan.
Both categories are lead acid, just in case you meant FLA specifically.
luthj
Engineer In Residence
AGM/sealed batteries with catalysts will not typically vent (in my experience), even if left at 14.4-14.6V for extended periods, assuming the ambient temps are not extreme, and the battery is not damaged. I say typically, as some cheaper sealed batteries will have little or no catalyst, or may have weaker cases, and thus vent at very low internal pressures. I will see if I can find some of the research I have saved, but even when abusively charged, most quality AGMs will loose maybe a few grams of electrolyte per cycle (this is charging at 1C and using current differential to terminate, so often 15V or higher).
Maintenance free cheap sealed (but still flooded) batteries will typically vent during extended charging like the above, because they often lack catalysts in the caps/lid.
Extended charging at high voltages (basically floating at that level) will cause degradation through plate and grid breakdown. This is why float service standby/backup battery packs are floated at a lower voltage.
My point is that a few hours here or there sitting at absorb and 100% full won't cause rapid degradation of the battery.
Maintenance free cheap sealed (but still flooded) batteries will typically vent during extended charging like the above, because they often lack catalysts in the caps/lid.
Extended charging at high voltages (basically floating at that level) will cause degradation through plate and grid breakdown. This is why float service standby/backup battery packs are floated at a lower voltage.
My point is that a few hours here or there sitting at absorb and 100% full won't cause rapid degradation of the battery.
No not rapid. And no worries if only occasional.
When using charge sources with a timer-based AHT adjustment, 99.9% of them, as opposed to reading trailing amps directly
you rarely will hit it just right, either a bit too long or a bit premature.
Chronically going to Float early, is worse than going over by a bit, even half the time.
But chronically going too long every time needs to be avoided too.
And AHT required can vary by usage patterns, seasons too.
When using charge sources with a timer-based AHT adjustment, 99.9% of them, as opposed to reading trailing amps directly
you rarely will hit it just right, either a bit too long or a bit premature.
Chronically going to Float early, is worse than going over by a bit, even half the time.
But chronically going too long every time needs to be avoided too.
And AHT required can vary by usage patterns, seasons too.
Yes the G31 datasheet illustrates the dramatic effect dod has on cycle life, for my application dod hasn’t exceeded 30-40% (with the exception of capacity testing)
I think a 1.5A cutoff is more reasonable than 0.6A. My G31 just finished a charge and is floating at 0.3A @13.4V. So with some tolerance on the current cutoff setpoint it would indeed be very easy to miss.
I think a 1.5A cutoff is more reasonable than 0.6A. My G31 just finished a charge and is floating at 0.3A @13.4V. So with some tolerance on the current cutoff setpoint it would indeed be very easy to miss.