If you're doing it with springs it'll be compressed either way.Getting new 280ah prismatic cells. Should I compress them when charged or discharged?
Using the aluminum plate with end springs.
Mine bulge not in the center, but on the two off center areas where the jelly roll is folded to make the 180 turn.However, it does not directly translate when you consider that the cells bulge from the center.
This is not correct. The PSI that the force was converted into was done so by taking the force they were using and dividing it by the surface area of the wide side of a 280AH cell.PSI vs kgf is irrelevant however (as it’s the same).
If you want to be crazy about it, after have done everything and are ready to put them into service, set your spring length for your desired force at 50% SOC and if you have no compressible foams in the system, forget about it. If you have any compressible foams anywhere in your assembly, reset it again in a month or so and then forget about it.Getting new 280ah prismatic cells. Should I compress them when charged or discharged?
Using the aluminum plate with end springs.
It really doesnt matter where or how many bulges there are, they do not expand and contract uniformly which is the point.Mine bulge not in the center, but on the two off center areas where the jelly roll is folded to make the 180 turn.
100%. I said exactly that in post #156I did some research a while back trying to find a suitable bladder to maintain 12PSI but couldn't find anything I liked.
I do agree that EVE is probably testing in a rigid fixture ... but this can be corrected by putting a piece of rigid material between the bladder and the cell .... then, the Kgf and 12PSI WOULD be the same thing.
I just thought I'd point that out, since you seemed to state it as fact to back up your statement that air pressure can't deliver.It really doesnt matter where or how many bulges there are, they do not expand and contract uniformly which is the point.
I did some research a while back trying to find a suitable bladder to maintain 12PSI but couldn't find anything I liked.
I do agree that EVE is probably testing in a rigid fixture ... but this can be corrected by putting a piece of rigid material between the bladder and the cell .... then, the Kgf and 12PSI WOULD be the same thing.
A bladder will absolutely deliver uniform pressure to the surface of the cell. What I am trying to say is that uniform pressure on every square millimeter of surface on the cell is not what you want (based on what I read from that report/study). What I interpreted from that paper is you want to apply a force to the surface (through a flat plate) to prevent any area of the cell from swelling. This will result in higher pressures in some locations and lower in others as the swelling is not uniform.I just thought I'd point that out, since you seemed to state it as fact to back up your statement that air pressure can't deliver.
Personally, from my point of view, using an air bladder has drawbacks, but uniform pressure isn't one of them.
Agree.That’s exactly what I meant. For the given surface area it’s the same. As to what’s happening between the rigid material and the cell at various locations, that’s a different issue.
Do you have a link or reference to the report you are talking about?A bladder will absolutely deliver uniform pressure to the surface of the cell. What I am trying to say is that uniform pressure on every square millimeter of surface on the cell is not what you want (based on what I read from that report/study). What I interpreted from that paper is you want to apply a force to the surface (through a flat plate) to prevent any area of the cell from swelling. This will result in higher pressures in some locations and lower in others as the swelling is not uniform.
If china has wanted uniform pressure applied to the surface of the cell, they would have used a units of pressure, not "kg of force"
The report/test that was done by EVE ( I think) that started this whole compression thing. I dont have it readily available. I got what I needed and moved on.Do you have a link or reference to the report you are talking about?
Sorry if you've already posted that, but I couldn't find it and am interested to understand this aspect of compression.
What I remember seeing from EVE is simply the information in their specification that shows the benefits of compression on cycle life ..... and a post from ghostwriter66 who had a conversation with one of the EVE engineers which brought out more details.The report/test that was done by EVE ( I think) that started this whole compression thing. I dont have it readily available. I got what I needed and moved on.
Beyond that, I would put into the area of theory or speculation.
Is it possible that a soft bladder with 12PSI might be even better .... I don't know .... If there is a document that shows the pressure must be from a rigid plate, I would really like to have it for reference.
LOL on the punWhat I remember seeing from EVE is simply the information in their specification that shows the benefits of compression on cycle life ..... and a post from ghostwriter66 who had a conversation with one of the EVE engineers which brought out more details.
I don't remember anything specifically saying that the pressure on the cells is BETTER or only works if the pressure is from a rigid plate. I understand what you are saying about the uneven pressure a plate will provide ... might .... be necessary for the compression to do it's magic.
Don't get me wrong ... I have posted in the past that my assumption would be that is the way EVE is doing their testing with a solid plate .... and therefore that would be the most prudent way to do it.
Beyond that, I would put into the area of theory or speculation.
Is it possible that a soft bladder with 12PSI might be even better .... I don't know .... If there is a document that shows the pressure must be from a rigid plate, I would really like to have it for reference.
Not sure we can make rigid statements regarding this ... pun intended.
I was under the impression this is the most accurate information we have about how EVE accomplishes it:What I remember seeing from EVE is simply the information in their specification that shows the benefits of compression on cycle life ..... and a post from ghostwriter66 who had a conversation with one of the EVE engineers which brought out more details.
I don't remember anything specifically saying that the pressure on the cells is BETTER or only works if the pressure is from a rigid plate. I understand what you are saying about the uneven pressure a plate will provide ... might .... be necessary for the compression to do it's magic.
Don't get me wrong ... I have posted in the past that my assumption would be that is the way EVE is doing their testing with a solid plate .... and therefore that would be the most prudent way to do it.
Beyond that, I would put into the area of theory or speculation.
Is it possible that a soft bladder with 12PSI might be even better .... I don't know .... If there is a document that shows the pressure must be from a rigid plate, I would really like to have it for reference.
Not sure we can make rigid statements regarding this ... pun intended.
I think your impression is correct.I was under the impression this is the most accurate information we have about how EVE accomplishes it:
EVE-280 cells should these be clamped tight or spaced for expansion?
Do any of them tell you what state of charge the cells should be in when you apply the 12psi? I tightened mine until my lock washers were flat. That is exactly 12psi All the of the people I trust say that the batteries should be at a low state of charge. Like just before you would recharge them...diysolarforum.com