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Cinergi's 28 kWh / 4 kW Solar / 10 kW inverter RV build

Solarfun4jim said:
What was your reasoning for discharging to 2.0v/cell? I know you must have had a good reason, but i always thought 2.5v/cell was the cut off point for these type cells?
I may have missed some of your discussion on this previously....but i'd be interested to know.
Click to expand...

It's one of the birds I'm killing with one stone. The reseller asked me to do that on my "bad" cells and then to charge and repeat my capacity test.
 
cinergi said:
It's one of the birds I'm killing with one stone. The reseller asked me to do that on my "bad" cells and then to charge and repeat my capacity test.
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wow...i always thought damage was done below 2.5v. Did they attempt to explain the technicalities behind this....that would be good info to know.
 
Solarfun4jim said:
wow...i always thought damage was done below 2.5v. Did they attempt to explain the technicalities behind this....that would be good info to know.
Click to expand...
We have been working with the supplier on this for some time now. This discharge to 2v was their most recent suggestion. All they said is:
"I ask the engineer, you can tell the customer, try to discharge to 2.0v, and see the capacity again"
 
This will be interesting. It's my understanding discharging a cell too much will reduce the capacity. I have no understanding how capacity would be increased. I don't know the threshold when damage starts below 2.5 volts, but there is a lot of difference between 2 and 2.5 volts. Also I don't know what effect this would have on cycle life. Is the supplier going to take liability if any damage is done to the cells?

These questions should have been addressed directly with EVE. I don't trust the suppliers "engineer" since no more information was provided. I hope I am wrong.
 
Gazoo said:
This will be interesting. It's my understanding discharging a cell too much will reduce the capacity. I have no understanding how capacity would be increased. I don't know the threshold when damage starts below 2.5 volts, but there is a lot of difference between 2 and 2.5 volts. Also I don't know what effect this would have on cycle life. Is the supplier going to take liability if any damage is done to the cells?

These questions should have been addressed directly with EVE. I don't trust the suppliers "engineer" since no more information was provided. I hope I am wrong.
Click to expand...
It is my understanding that these cells can be drawn down to zero, but repeatedly doing so will limit the number of cycles.
He is only doing it with his weakest 4 cells, so it is not the huge risk it would be otherwise.
If the engineer gave us all of the technical details, we still wouldn't now if we could trust what they say, so we would still be taking the same risk.
If damage is done to the cells by doing this one time, yes I will hold the supplier accountable and cinergi knows that I will take care of him even if the supplier does not. Refusing to take the steps the supplier asks us to would drastically limit the leverage we would have to demand suitable compensation from the supplier if the cells remain at too low of a capacity.
 
ArthurEld said:
It probably won't kill the cell to discharge it to 2V but there aren't any Ah between 2.5V and 2V.
So, I am doubting that is going to make a difference.
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I have my doubts as well. But, cinergi does not mind jumping through this hoop and so we will.
I did tell him that if he was tired of dealing with all of their suggestions I would tell them no and force the issue of compensation now, but he said it was no problem to give it a try.
 
Michael B Caro said:
It is my understanding that these cells can be drawn down to zero, but repeatedly doing so will limit the number of cycles.
He is only doing it with his weakest 4 cells, so it is not the huge risk it would be otherwise.
If the engineer gave us all of the technical details, we still wouldn't now if we could trust what they say, so we would still be taking the same risk.
If damage is done to the cells by doing this one time, yes I will hold the supplier accountable and cinergi knows that I will take care of him even if the supplier does not. Refusing to take the steps the supplier asks us to would drastically limit the leverage we would have to demand suitable compensation from the supplier if the cells remain at too low of a capacity.
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That's a fair response....removing the ultimate risk from cinergi. This is great info to have on the resulting outcome. (y)
Well done Michael. That buys you a lot of trust in my books.
 
Solarfun4jim said:
That's a fair response....removing the ultimate risk from cinergi. This is great info to have on the resulting outcome. (y)
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I assume as much risk as I possibly can for anyone that orders through me. I try to do for them what I would expect someone to do for me if I were on the other side of the table. I will not claim that there may not come a time when what the buyer thinks should be done differs from what I would expect if I were him, but I guarantee, at least from the situations I have run into so far, that I go above and beyond what the suppliers I have been working with do.
 
Solarfun4jim said:
What was your reasoning for discharging to 2.0v/cell? I know you must have had a good reason, but i always thought 2.5v/cell was the cut off point for these type cells?
I may have missed some of your discussion on this previously....but i'd be interested to know.
Click to expand...
Solarfun4jim said:
wow...i always thought damage was done below 2.5v. Did they attempt to explain the technicalities behind this....that would be good info to know.
Click to expand...
Michael B Caro said:
All they said is: "I ask the engineer, you can tell the customer, try to discharge to 2.0v, and see the capacity again"
Click to expand...
Gazoo said:
These questions should have been addressed directly with EVE. I don't trust the suppliers "engineer" since no more information was provided. I hope I am wrong.
Click to expand...
Michael B Caro said:
If the engineer gave us all of the technical details, we still wouldn't now if we could trust what they say, so we would still be taking the same risk.
Refusing to take the steps the supplier asks us to would drastically limit the leverage we would have to demand suitable compensation from the supplier if the cells remain at too low of a capacity.
Click to expand...
Some thoughts:
  1. Risk of significant damage from a single cycle down to 2.0V is higher than 2.5V, but maybe not excessively risky for someone as attentive (and at this point intimately familiar with his cells) as @cinergi. 2.5V is the minimum voltage as defined by the manufacturer (nearly all manufacturers), but in a academic/research context cells are routinely taken down to 2.0V.
  2. At the same time, reseller's "engineer" (<--more on that below) is asking a customer to take their cells below the manufacturer's limits, to a voltage that might possibly even void the warranty if it were a new warrantied cell, without indicating why.
  3. What would be the upside of finding 20Ah hiding down there? It would still not be usable capacity, the 280Ah minimum is defined as being between 2.5 and 3.65/0.05C
  4. I agree with @Michael B Caro that the "engineer" providing more technical details would not make us automatically trust them, but I agree with @Gazoo that providing at least some amount of technical information and explanation would go along way to establishing at least a little bit of trust. Maybe what they are advocating is a well established troubleshooting step, or maybe its akin to "IDK maybe if he discharges lower there will be more capacity, worth a try"
  5. On the term "engineer," I have heard (but don't know for sure), the way the resellers reference 'the engineer' is very different than what we might think it means and certainly different than a university would define the term. That said, I think there is much variation between resellers and I won't rule out that there may be a few with an actual engineer on staff (maybe), and I suspect many where is a rhetorical tool not a person, and many where it means something along the lines of "our tech person / tech support person." I don't think its realistic or even necessary for every seller of discount cells to have an actual engineer on staff, I just think we need to be conscious that 'engineer' doesn't necessarily mean engineer. Of course you have more familiarity with the resellers you buy from so you may have more insight/info.
  6. The fact that this is all only for @cinergi's 4 weakest cells makes it low risk in his case.
  7. As to refusing to take steps a supplier asks for: refusing outright maybe, but asking for explanation of any troubleshooting step but especially one that violates manufacturer limits, is not unreasonable, and is well short of refusal.
  8. @cinergi deserves an award for 2nd best customer for all the time and effort, and good will, and flexibility! (first place (from the resellers point of view) of course goes to the many hundreds of people who bought (and still buy) cells without testing or verifying anything and just chose to believe/profess that they got Grade A cells without testing)
  9. Final thought, I wonder if there is some logic behind this troubleshooting step that we could learn from. Some muse that the occasional full cycle up to 3.65 is good for maintaining capacity over time. Others say this is BS. Some have said they found a little extra capacity after a few cycles. But I've never heard anyone advocate an especially deep discharge to increase capacity (in the normal bandwidth limits) and I have no idea if this is the resellers logic or not. It would be interesting to know the why and the how behind this troubleshooting step. If there was any logic to it, it could help others. But as @Gazoo mentioned, it would be more reassuring to hear it from EVE or an academic source. Still following up for an explanation could benefit others.
edit: ahh man.. I wrote another DZL / Steve S -- borderline Fhorst / Jeephammer length comment.. sorry guys :) I've noticed a correlation between me starting a comment with "some thoughts" or "a few things to consider" and writing way too much. :rolleyes:
Hiding the ramble behind a spoiler tag..
 
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Michael B Caro said:
I assume as much risk as I possibly can for anyone that orders through me. I try to do for them what I would expect someone to do for me if I were on the other side of the table. I will not claim that there may not come a time when what the buyer thinks should be done differs from what I would expect if I were him, but I guarantee, at least from the situations I have run into so far, that I go above and beyond what the suppliers I have been working with do.
Click to expand...
In no way did I mean to imply you don't take care of anyone buying cells from you. I know you do, always have and always will. I trust you, and have trusted you 100%. I am sorry if you took anything I said differently, even a little bit. It's the suppliers I don't place 100% trust in and by suppliers I mean all of them, although some are better than others. But you are the best... :)
 
Gazoo said:
In no way did I mean to imply you don't take care of anyone buying cells from you. I know you do, always have and always will. I trust you, and have trusted you 100%. I am sorry if you took anything I said differently, even a little bit. It's the suppliers I don't place 100% trust in and by suppliers I mean all of them, although some are better than others. But you are the best... :)
Click to expand...
Nope. Didn't take offense at all....not sure what I said that made you think I might have. If I had took offense, you would have known about it, in no uncertain terms LOL. But in a "conversation", not out in public. ;)
 
cinergi said:
It was under 1Ah between 2.5 and 2.0 volts. Which is why I don't believe it's particularly damaging because we didn't really extract that many more electrons / move that much more LiFe around... and I immediately started charging the cells.
Click to expand...
I am anxiously waiting for your results. Are you done charging yet...lol. Seriously thanks for all your updates.
 
The one comment I will pull out of my self imposed spoiler quarantine, is that: if there is actually some logic/science behind the discharge down to 2.0V beyond ('its worth a try') it may benefit us and others to understand that logic. Some people (that I mostly trust, but aren't infallable) have observed positive benefits to completing full cycles to ~3.65 every so often. But I've never heard of anyone even muse about the opposite (full--or in this case 'over'--discharge) having any benefit whatsoever. Maybe they just want to test a lower voltage to rule out any slight measurement errors.
 
Dzl said:
The one comment I will pull out of my self imposed spoiler quarantine, is that: if there is actually some logic/science behind the discharge down to 2.0V beyond ('its worth a try') it may benefit us and others to understand that logic. Some people (that I mostly trust, but aren't infallable) have observed positive benefits to completing full cycles to 3.65 every so often. But I've never heard of anyone even muse about the opposite (full--or in this case 'over'--discharge) having any benefit. Maybe they just want to test a lower voltage to rule out any slight measurement errors.
Click to expand...
Maybe. I am not much of a technical guy. It took me a while to even look into "desulfating" with FLA batteries. lol
 
Below 2.5V there is less than 0.2% lithium ions left to move IIRC. I have not seen any research supporting going that low for any reason.
 
Perhaps @Dzl is referring to the formation process that is typically done at the factory?
This is pure speculation, but if these cells are culled after first formation charge at the factory, perhaps there is some benefit of doing that one or two times more? @Steve_S has talked about the benefits of "trash testing" these cells. Other than that wild ass speculation. I would not be doing that to my cells. I am comfortable only using 80% of these cells capacity and only going from 3.0 to 3.4 volts.
 
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Dzl said:
The one comment I will pull out of my self imposed spoiler quarantine, is that: if there is actually some logic/science behind the discharge down to 2.0V beyond ('its worth a try') it may benefit us and others to understand that logic. Some people (that I mostly trust, but aren't infallable) have observed positive benefits to completing full cycles to ~3.65 every so often. But I've never heard of anyone even muse about the opposite (full--or in this case 'over'--discharge) having any benefit whatsoever. Maybe they just want to test a lower voltage to rule out any slight measurement errors.
Click to expand...

That's one of the reasons I chose to do this - I want to see if there's any truth to this.
 
Ampster said:
Perhaps @Dzl is referring to the formation process that is typically done at the factory?
Click to expand...
Which of my comments are you referring to? This one?:
Risk of significant damage from a single cycle down to 2.0V is higher than 2.5V, but maybe not excessively risky for someone as attentive (and at this point intimately familiar with his cells) as @cinergi. 2.5V is the minimum voltage as defined by the manufacturer (nearly all manufacturers), but in a academic/research context cells are routinely taken down to 2.0V.
Click to expand...
If this is what you were referring to, I only mean that in many of the research papers I have encountered for the purposes of testing/research only, they often take cells down to 2.0V or thereabouts. This is not to say they or anyone else reccomends it, or that it won't harm the cells, or shorten cycle life (it might, that isn't really a concern for researchers just looking to test some hypothesis or another, cells are expendable in that context). So to be crystal clear. Saying researchers do it is in no way saying its advisable or that researchers condone it. I would not go below 2.5ish volts personally, at least not without being convinced of a very good reason. And I want to make sure my comment isn't misunderstood as condoning intentionally exceeding manufacturer defined limits.

I may have misunderstood what you were referencing but I wanted to nip it in the bud if it relates to the 2.0V thing.
 
Dzl said:
Which of my comments are you referring to? This one?:
Click to expand...
I was referring to the comment that @cinergi quoted above that reminded me of what @Steve_S was doing. I made my own connection of that to the formation process done at the factory. My response was off the cuff and actually a sidetrack from meat of the 2 volts discussion. I have not done the kind of trash testing that Steve has done and am happy only using 80% of the capacity of my cells.
 
Pinged 2x:
My thrash testing was only between 2.500-3.650 and not beyond specifications for Charger/Discharge rates.
I did not read this thread here for quite a while. (not following threads) so I'm now aware of the content of the ongoing discussion.
I can say, that Capacity retention improved "slightly" after 2 deep, top to bottom cycles, the AT REST voltage (post charge settling) only went up on average of 150mv.
Between 3.00-2.500 and 3.450-3.650 is really minimal AH. On 280's my observed guesstimate it's likely not more than 10-13AH at best.

I dunno if that helps at all.
Steve
 
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