For your 1/4 rod with the spring just put a sleeve on the rod so the tread will not affect the mouvement when the spring is expendingOK, discharged to 0% (2.000 volts each actually). Raw numbers are below. I'm pretty sure I heard the springs a few times. Maybe I'll capture a time-lapse of this some day. These springs really should have a 3/8" rod between them (not 1/4" like I do). The springs are deforming a bit as a result.
Summary: The top springs expanded by about 1.7mm and the bottom springs by about 2.7mm. The terminals, after I removed the bus bars, were closer together (anywhere from 0.11mm to 0.96mm). My measurements were a little faulty there but it's obvious they got closer.
I think it's pretty clear that the solid bus bars are put under strain in this situation and prevent the compression fixture from evenly compressing (the top didn't compress as much as the bottom).
I will measure again after I recharge the battery.
At 100% SoC
============
Terminals
77.98
78.65
78.20
78.75
77.87
78.14
Springs
26.72 ("top left")
27.11 ("bottom left")
27.12 ("top right")
27.48 ("bottom right")
At 0% SoC
============
Terminals
77.65 (-0.33)
77.69 (-0.96)
77.80 (-0.60)
77.97 (-0.78)
77.51 (-0.36)
78.03 (-0.11)
Springs
28.46 (+1.74)
29.75 (+2.64)
28.78 (+1.66)
30.24 (+2.76)
For your 1/4 rod with the spring just put a sleeve on the rod so the tread will not affect the mouvement when the spring is expending
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?OK, discharged to 0% (2.000 volts each actually).
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.
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.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.
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: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.
It is my understanding that these cells can be drawn down to zero, but repeatedly doing so will limit the number of cycles.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.
I have my doubts as well. But, cinergi does not mind jumping through this hoop and so we will.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.
That's a fair response....removing the ultimate risk from cinergi. This is great info to have on the resulting outcome.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.
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.That's a fair response....removing the ultimate risk from cinergi. This is great info to have on the resulting outcome.
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.
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.
All they said is: "I ask the engineer, you can tell the customer, try to discharge to 2.0v, and see the capacity again"
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.
Some thoughts: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.
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...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.
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.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...