Compress or not, flexible busbar or not

[noenegdod]

This is going nowhere.

Quoted for truth! This is about as productive as most of the threads in the off topic section discussing religion and politics.

 

[Cheap 4-life]

Kgf / what unit?

Kilograms of force

 

[noenegdod]

Try to hold two steel plates on each side of one cell and keep it from expanding thru an entire SOC (if that was possible) and now try to do the same thing with 8 cells and you tell me which one requires more pressure/compression to do so.

This is exactly what we are trying to tell you and your not listening. They will experience exactly the same pressure/force.

 

[noenegdod]

but I’d think it would still take more than 12psi to keep 8 cells flat if it only took 12psi to keep one flat. How much more idk.. Meaning that in a rigid fixed case the endplates would see more pressure/psi with 8 cells at 100% SOC than 1 cell at 100% SOC.

NO! it will be exactly the same.

 

[Cheap 4-life]

Quoted for truth! This is about as productive as most of the threads in the off topic section discussing religion and politics.

Look there’s no reason for people not compressing or people compressing or springs or foam or popsicle sticks or cutting boards etc etc to not get along here. It’s simply opinions from whoever wants to comment. I spent much of my free time the last two weeks reading basically all the info/comments/opinions/facts on this forum regarding this issue.. anyone can take what they want from this thread or contribute or move on.. this is absolutely an issue that’s not one sided or heavily agreed upon

 

[noenegdod]

Try to hold two steel plates on each side of one cell and keep it from expanding thru an entire SOC (if that was possible) and now try to do the same thing with 8 cells and you tell me which one requires more pressure/compression to do so. You might get both sides of one cell to stay flat but if you tried to do that with 8 cells you might get the outside cells outside walls flat but not flatten the interior cells at all because it would require more pressure because more cell walls and cell expansion is causing more pressure needed to achieve the same flatness that is seen when only one cell was squeezed.. I’m not saying that if it took12psi to keep one cell flat that it will take 96psi to keep 8 cells flat, but I’d think it would still take more than 12psi to keep 8 cells flat if it only took 12psi to keep one flat. How much more idk.. Meaning that in a rigid fixed case the endplates would see more pressure/psi with 8 cells at 100% SOC than 1 cell at 100% SOC.
I mean when you compressed 4 cells for your clamp for your foam rig, was it easier than when you compressed 8cells with the same clamp?

If you take 1 hydraulic ram and put it between two objects it will apply a given force. If you take two hydraulic rams and put them side by side they will apply twice that given force. HOWEVER, if you put the second ram in line with the first ram so they are pushing inline with each other they will only produce the given force. It is not a multiple it is exactly the same as the given force of the one ram. The cells are the same. 1 cell, 1,000 cells. Same force.

 

[noenegdod]

Look there’s no reason for people not compressing or people compressing or springs or foam or popsicle sticks or cutting boards etc etc to not get along here. It’s simply opinions from whoever wants to comment. I spent much of my free time the last two weeks reading basically all the info/comments/opinions/facts on this forum regarding this issue.. anyone can take what they want from this thread or contribute or move on.. this is absolutely an issue that’s not one sided or heavily agreed upon

When your not only ignoring but arguing against basic physics it makes it difficult to take you seriously.

If you spent 2 weeks reading about this subject why are you still talking about it. Start building!

 

[Cheap 4-life]

If you take 1 hydraulic ram and put it between two objects it will apply a given force. If you take two hydraulic rams and put them side by side they will apply twice that given force. HOWEVER, if you put the second ram in line with the first ram so they are pushing inline with each other they will only produce the given force. It is not a multiple it is exactly the same as the given force of the one ram. The cells are the same. 1 cell, 1,000 cells. Same force.

So let’s use your hydraulic ram. If that ram pressed with just enough force to keep one cell flat at 100% SOC. Would that ram be able to keep 8 cells at 100% SOC just as flat as it did the one cell using only that same exact amount of force? I’m not saying ending up at the same psi. I’m saying the same amount of force. because that’s what’s applied to the rigid walls. I’d think it would take more force same as more force would be applied to the rigid walls to create the same psi in the 8cell vs 1 cell pack

 

[Cheap 4-life]

When your not only ignoring but arguing against basic physics it makes it difficult to take you seriously.

If you spent 2 weeks reading about this subject why are you still talking about it. Start building!

I’m ok with your opinions, I’m not ignoring or arguing, simply typing my point which you do not agree with which again is fine, we all can’t agree and even agree less on this highly debatable subject.. but since your implying that I’m doing something wrong, then heres what your doing wrong. Getting aggravated because we have a difference in opinion. You are making implications about the data sheet that imo do not make sense but go along with your opinion that a fixed/rigid fixture is fine.

 

[42OhmsPA]

Kilograms of force

Yes, kgf is kilograms of force. My question is kgf over what surface area? Are they using sq. M,cm,mm?
Did you look at the screenshots I posted?
300 kgf/sq.cm = 4267psi (pounds per square inch) 300 kgf / sq.m = 0.4267 psi.
I can't find anything in the data sheet, it's quite relevant for creating fixtures.

 

[Cheap 4-life]

There is no absolute proof (thru the entire SOC) that putting 16 280ah cells together isn’t exerting more force on the endplates (of a rigid/fixed rig with solid walls or with threaded rod) than the force 1 cell is exerting on its end plates.. none that I have read anyways.
Although I have read of a few times when people compressed 16 cells with 660lbs or so of force and the cells still expanded a lot causing solid busbars to loosen, bms issues etc

 

[42OhmsPA]

So let’s use your hydraulic ram. If that ram pressed with just enough force to keep one cell flat at 100% SOC. Would that ram be able to keep 8 cells at 100% SOC just as flat as it did the one cell using only that same exact amount of force? I’m not saying ending up at the same psi. I’m saying the same amount of force. because that’s what’s applied to the rigid walls. I’d think it would take more force same as more force would be applied to the rigid walls to create the same psi in the 8cell vs 1 cell pack

That depends if the ram can withstand the pressure created by the additional cells expansion while still maintaining the force.

 

[Cheap 4-life]

That depends if the ram can withstand the pressure created by the additional cells expansion while still maintaining the force.

Which is the same as saying if the endplates can withstand the pressure created by the additional 7 cells which is my point unless I’m still missing something

 

[42OhmsPA]

There is no absolute proof (thru the entire SOC) that putting 16 280ah cells together isn’t exerting more force on the endplates (of a rigid/fixed rig with solid walls or with threaded rod) than the force 1 cell is exerting on its end plates.. none that I have read anyways. Although I have read of a few times when people compressed 16 cells with 600lbs or so of force and the cells still expanded

Difference Between Force and Pressure | Compare the Difference Between Similar Terms

Force vs Pressure Force and pressure are two important concepts in the study of motion in physics. While there are many similarities in force and pressure,

www.differencebetween.com

 

[Cheap 4-life]

Yes, kgf is kilograms of force. My question is kgf over what surface area? Are they using sq. M,cm,mm?
Did you look at the screenshots I posted?
300 kgf/sq.cm = 4267psi (pounds per square inch) 300 kgf / sq.m = 0.4267 psi.
I can't find anything in the data sheet, it's quite relevant for creating fixtures.

Idk, but 300kgf is like 660lbs which with springs is roughly 165lbs per spring

 

[Cheap 4-life]

Difference Between Force and Pressure | Compare the Difference Between Similar Terms

Force vs Pressure Force and pressure are two important concepts in the study of motion in physics. While there are many similarities in force and pressure,

www.differencebetween.com

Right so it takes more force to keep 16cells from expanding than it does to keep one cell from expanding.. and that force/mass from all the cells walls expansion (more force the more cells) is applied to the end plates which creates more pressure/psi throughout the rig which is why the psi each cell experiences (or force if you want to look at it that way) rises as the SOC rises. Which is why a rigid/fixed rig can get people in trouble the more cells they put in a fixed rig. That’s why I chose springs

 

[Cheap 4-life]

If you take 1 hydraulic ram and put it between two objects it will apply a given force. If you take two hydraulic rams and put them side by side they will apply twice that given force. HOWEVER, if you put the second ram in line with the first ram so they are pushing inline with each other they will only produce the given force. It is not a multiple it is exactly the same as the given force of the one ram. The cells are the same. 1 cell, 1,000 cells. Same force.

My understanding is having one hydraulic ram behind another will indeed create more force. In a diy battery pack the pressure is held/applied by the endplates that could be fixed with a rigid rig. So the more cells the more force applied to the endplate therefore more pressure through the cells. Which is why a higher pressure is experienced by each cell as the cell gets a higher SOC in a compressed/fixed/rigid inclosure..
Or how I like to look at it. If I’m pushing on a car trying to move it (like I’m one cell trying to expand) and my equally strong buddy (second cell trying to expand) pushes on my back, we will create more force/mass therefore more easily moving the car. Now if that car was against a concrete wall (like cells against fixed rigid end plates) then my buddy and I would simply be exerting our force against the concrete wall, which is more force than I could put on the concrete wall if I was the only pusher.. which would create a higher psi at the concrete wall..
Point is 2 cells (2 people) apply more force to the end plate (concrete wall) than one cell (one person would), which creates more pressure throughout the rig or throughout the push/SOC.
Since my buddy is pushing on my back it’s not double the force as it would be if he was pushing aside of me but it’s still more force with two of us like it would be with 1 cell against another cell, which makes more force than just one cell.
I might not have went to college but I have pushed a lot of cars..

 

[justgary]

I mean when you compressed 4 cells with your clamp for your foam rig, was it easier than when you compressed 8cells with the same clamp?

No. That's the whole point. The force is exactly the same with one, four, eight, or more.

 

[Cheap 4-life]

No. That's the whole point. The force is exactly the same with one, four, eight, or more.

That might be your entire point but maybe (bare with me here) you were overlooking how much more force was involved to compress 8 cells instead of 4 because of your view point. Did you read post #237. Am I wrong?

 

[justgary]

Think of compression force in a group of cells in exactly the same way as the charge current in that group if they are wired in series. It is constant no matter how many are in the group.