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EVE LF280 arrived damaged.

OK - i had to delete my first response(s)(s) -- deep breath -- WHAT ARE YOU BASING THIS ON???
I am basing it on the EVE spec sheet. There are may discussions about how to do this in the forum. I asked EVE and they basically told me to mount the cells in a fixture to keep them from expanding. It helps to keep the pouch within the aluminum case from delaminating.

I will be using .5 inch plywood and threaded rods. Since I top balanced with no compression I am going to drain the pack down then tighten the nuts so they are snug. BTW Lishen also says the same thing in their spec sheet for the 272 amp cells.
 
It's in the latest eve lf280N data sheet. Bottom of section 6

Not arguing the compression theroy -- arguing that you can go from 2500 to 3500 cycles if you put the battery under 300kgf of force. I am going to call them Sunday night (my time) and see how they came up with that cycle number and kgf ...

How did they get that 2500 to 3500 number is my question ...

300kgf - if i am doing my math right .. equals ~662 POUNDS of force.... that's pretty snug .. can you even compress plywood that much??
 
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Not arguing the compression theroy -- arguing that you can go from 2500 to 3500 cycles if you put the battery under 300kgf of force. I am going to call them Sunday night (my time) and see how they came up with that cycle number and kgf ...

How did they get that 2500 to 3500 number is my question ...

300kgf - if i am doing my math right .. equals ~662 POUNDS of force.... that's pretty snug
I've interpreted that as an enclosure that can withstand 300kgf. But then I suspect at that force the sides would pop? Anyway, mine are going between two end plates of 10mm aluminium plate and 8 no. 6mm stainless threaded rods to hold them together. ??‍♂️
 
Not arguing the compression theroy -- arguing that you can go from 2500 to 3500 cycles if you put the battery under 300kgf of force. I am going to call them Sunday night (my time) and see how they came up with that cycle number and kgf ...

How did they get that 2500 to 3500 number is my question ...

300kgf - if i am doing my math right .. equals ~662 POUNDS of force.... that's pretty snug .. can you even compress plywood that much??
I will be interested what they tell you vs. what they told me. Please let us know.
 
I've interpreted that as an enclosure that can withstand 300kgf. But then I suspect at that force the sides would pop? Anyway, mine are going between two end plates of 10mm aluminium plate and 8 no. 6mm stainless threaded rods to hold them together. ??‍♂️

From the datasheet "The battery cell is under the action of preset 300kgf force" ... that means that there is a 300kpf force pressing on the battery - squeezing it ... They are recommending 662 lbs ... my torque wrench here at work only goes to 600 and honestly - its as tall as i am and i have to get one of the bigger guys to do anything over 150 so I can only imagine 662... Our DIESEL GENERATOR bolts goes in at 600 ...

Another question for them is what are the breakaway numbers?? .. meaning .. if we get 3500 cycles at 300kpf, then what increase would we get at 200 or 100kpf, if anything.
 
From the datasheet "The battery cell is under the action of preset 300kgf force" ... that means that there is a 300kpf force pressing on the battery - squeezing it ... They are recommending 662 lbs ... my torque wrench here at work only goes to 600 and honestly - its as tall as i am and i have to get one of the bigger guys to do anything over 150 so I can only imagine 662... Our DIESEL GENERATOR bolts goes in at 600 ...

Another question for them is what are the breakaway numbers?? .. meaning .. if we get 3500 cycles at 300kpf, then what increase would we get at 200 or 100kpf, if anything.
I think their figures are dubious, the cells would split at that force. I will be snugging the nuts until they are just tight, I'm a recovering over torquer'. I will happily cherry pick their info and just go with keeping them compressed makes them last longer. Will be interested what they say to you though. It's often a long chain between who you speak to and who knows wtf the specs mean.
 
From the datasheet "The battery cell is under the action of preset 300kgf force" ... that means that there is a 300kpf force pressing on the battery - squeezing it ... They are recommending 662 lbs ... my torque wrench here at work only goes to 600 and honestly - its as tall as i am and i have to get one of the bigger guys to do anything over 150 so I can only imagine 662... Our DIESEL GENERATOR bolts goes in at 600 ...

Another question for them is what are the breakaway numbers?? .. meaning .. if we get 3500 cycles at 300kpf, then what increase would we get at 200 or 100kpf, if anything.
The torque on the bolts will be a lot less than the force exerted via the threaded rod and plywood .... There was another post about this where they actually determined the bolt torque need. I think it varies depending on size of threaded rod and thread count also.

I'll see if I can find that.
 
It the torque vs compression value was discussed pretty heavily in this thread.

 
Its fairly easy to get 600lbs of compression on the cells. I measured my 4 cell stack at that load, and there was no appreciable compression.

The fixture needs to prevent the cells from expanding (say 1-2mm) as they cycle up. Its easiest to just start at a similar load when new, and don't worry about it.

3/4" plywood and threaded rod will work just fine.

600lbf is probably the force needed to keep the cells from delaminating and voids forming at high cycle counts. Remember that's only ~10-15psi.
 
How is it possible to compress a pouch within a flat aluminum case? It can't be done. EVE told me mounting the cells in a fixture to keep them from expanding is all that is needed. This had been beat to death over and over. I am going to step back until we hear back from ghostwriter.

Dear sales:


Could you please explain the following quoted from your 280ah cell specification:

"At 25±2℃,the battery under 300kgf fixture : charging the cell with charge current 1.0C(A) and constant voltage 3.65V,0.05C cut off,rest for 30min,discharge to 2.5V cut off with the current of 1.0C(A),rest for 30min,and then start the next cycle,end with the capacity decrease to 80% of the initial capacity.The number of cycles is defined as the cycle life of the battery."

Why is a fixture required?

Is it to prevent expansion of the cells for longer cycle life?

If the cells are mounted in a fixture so they can not expand will that work?

Please reply and explain. Thank you.

EVES REPLY:

Hello,

Your understanding is right. During the charge & discharge process of battery, the cell will “breath” like people does- swell & shrink effect.

The function of fixture, we use the clamp, is to prevent the over-swelling effect, which is likely to cause electrolyte leak furthermore.

Thus the fixture will guarantee longer life.

Thank you & Best Regards


By electrolyte leak I believe they are referring to the pouch within the aluminum housing. Delamination.
 
What you want to do is to stop the insides from moving around and over the 10 years for 2,500 cycles to happen it will not fall apart inside.
By holding the sides firmly and preventing them from bulging and contracting repeatedly you prevent the insides from falling apart and thus the product lasts longer.
Kind of like closing your doors on your car when you do driving. Doing so makes them last longer is all.
So dep0lete the battery cells. Clamp them firmly [not crushing them], And then fill them up again and you are good to go.

Maybe this will make it easier. :)
 
I tightened mine until the lock washer was flat. I don't think the fixture is supposed to compress the cells.
It is supposed to keep the cells from expanding too much.
I read that if the cells are compressed, the capacity will be lower.
 
You know you have been out in the South Texas oil fields to long when you laugh at this - for all the wrong reasons ... :oops::oops:
Out there corrupting the innocent minds of all those poor gentle oil field workers, are ya

I am going to call them Sunday night (my time) and see how they came up with that cycle number and kgf ...
Who is the them in this case? EVE proper?
Look forward to hearing what they have to say if anything.


300kgf - if i am doing my math right .. equals ~662 POUNDS of force.... that's pretty snug ...
This was my reaction at first also, but once you spread it over the surface area of the broad side of a cell, it didn't seem so excessive, I don't recall what the value was, someone else might. But as Gazoo and others have previously noted, I think the main purpose is keeping the cells from expanding/bulging/deforming.
 
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I think that the purpose of saying it is 300kgf [or 602 pounds] is not to APPLY that amount so much as that the compression force should be able to RESIST that amount of force.
By being able to resist that amount of force it will stop the cells from expanding.
 
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