Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
- Messages
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What happens to spacing between terminals? What do you use for busbars?
How about 1/16" sheet for every cell, instead?
Another Cell Compression Thread, this time about foam
- Thread starter Zwy
- Start date
What happens to spacing between terminals? What do you use for busbars?
How about 1/16" sheet for every cell, instead?
Ron-ski
Solar Enthusiast
Ron-ski
Solar Enthusiast
Same here, an insulator should always be used between cells, I used 1mm epoxy sheets, these are supplied standard with a lot of cells nowadays, and certainly with good quality battery boxes.
My cells came with FR4 PC board material for spacers. I used Kapton tape on the narrow sides and bottoms.
I used braided flexible bus bars.
One would need to test the 1/16" foam to see if it is suitable. The force curve changes as you stack layers.
I used braided flexible bus bars.
One would need to test the 1/16" foam to see if it is suitable. The force curve changes as you stack layers.
this is exactly the type of logic and mindset that i already addressed. you must have missed that part of the whole discussion, which it was basically entirely about haha....
you think that eve posted the fixture parameters as if people are going to use these as a single cell?.... that all of the r&d that goes into it and the big brains that made it possible... you think they dont know that every single application that it will ever be used for will consist of a multiple-cell pack?
lets then look at all of the other companies that use prismatic cells, and the generous warranties they offer, and the reputation they put at stake.... do none of those companies know how to best assemble a pack? would they have not done the research and talk to the engineers before investing a mountain of money into designing packs with NO foam, spring, dampening, etc? but instead, they ALL use rigid compression...
ev's, home solar storage, golf carts, Marine....
every. single. one.
all of them.
and i believe his battery shelf has also suffered advanced degradation, and swelled to the point of his surprise.
could be wrong, but I'm pretty sure that was his shelf
Daddy Tanuki
Emperor Of Solar
they all need clamping and fixtures, Winstons answer was to sell a clamping fixture that was sized to the number of cells you planned on lining up. assemble the fixture they sold and your clamping was at their preferred setting. pretty easy to reverse engineer as well. does not matter if you use a compression foam, or springs, as long as it provides pressure in the desired range.
winston banding system:
winston banding system:
As mentioned a few posts back, that is the case now. Their recommendation was not that clear a few years ago.
i am not too* familiar with those cells, but those seem to be similar to the gen 1 calb cells, which have a thick rigid body, and therefore does not need to be compressed.
we are discussing the thin aluminum walled eve style cells, and they would deform if not compressed. different architecture.
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my statement did not have a time constraint. every manufacturer of battery packs using prismatic cells has used rigid mounting fixtures. every time.
not just in recent times.
Pierrot
New Member
- Joined
- Apr 21, 2020
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- 27
Hello, new battery packs manufacturers use adhesive eva foam + epoxy insulation sheets as dividers :
EEL V4 48V DIY Box
Yixiang 48V DIY Box
EEL V4 48V DIY Box
Yixiang 48V DIY Box
Daddy Tanuki
Emperor Of Solar
Oh so now you know more than the engineers that made them huh? sorry that kit I showed a photo of is from their brochure... it is an ad for their compression setup that they sell to match the cells and pack size.
those are not manufactured battery packs. those are boxes made to fit a variety of cells for people to assemble themselves. no warranty, no risk. they just need the cells to fit. i actually addressed these exact style of boxes in an early comment.
BUT eel actually does have a video of another product, and it is a pre-assembled pack... ill let you guess if they used foam or not....
they dont
no, and i literally began by saying the exact opposite of that... not really sure how you came to that conclusion, which is worrisome and brings into question the rest of your conclusions.
Daddy Tanuki
Emperor Of Solar
yes you did say the opposite but you had already went knee deep insinuating that they did not need to be compressed, I simply posted the proof that they do and then you decided that since you did not win that discussion you needed to move the goal posts. continue on, you jumped into a thread that was more or less finished and then started trash talking. do not be shocked when others treat you the same.
I suppose if you directly read Chinese you might have understood that. When I bought my cells, the only mention in the specification sheet was, "the battery under 300kgf fixture" and nothing more. Discussions here indicated that one of the members here contacted EVE and was told that too much compression was worse than not enough. Hence, 300kgf was taken to be the maximum. If you have a specification sheet from 2022 or before that clearly discusses compression, please share it.
Later specifications actually clarified the force as rigid compression and showed a drawing of the fixture. Some members here had trouble extrapolating from one cell to many cells, but the force is the same in all cells in the same fixture. I would not use Poron foam if I built a battery today.
The big problem I see with building a rigid fixture is actually getting the compression force set properly. It is relatively easy to calculate the distance needed to compress a spring or foam to the correct force, but it is not trivial to rig a hard fixture that lets one securely bolt an end cap at the exact distance needed to apply a specific force. If you know of a simple way to do that, please share it (and I don't think that measuring torque on bolts is accurate enough).
Ron-ski
Solar Enthusiast
That's what I often wonder about the DIY battery boxes, slap the cells in, insulation sheets Eva foam, and if your lucky the bolts are long enough to reach, but how tight do you tighten them?? It doesn't seem very precise, more hit and miss, and hope for the best.
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Daddy Tanuki
Emperor Of Solar
agreed. many of us have tried different ways if I was still in the cell ordering came i would just have paid the extra for the winston cell fixtures, I just did not like the fact that they only offered straight line, and wanted to double stack mine. regardless mine is less than the max and above zero, so its better than nothing. the winston fixture is a set force when the battery is at 30% as delivered from the factory. you then assemble it and top or depending upon use bottom balance the cells. but in the end the compression is fixed at the 30% SOC. This was mock up and the springs were not tensioned yet.
Bob B
Emperor Of Solar
- Joined
- Sep 21, 2019
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The most definitive answers I recall came out of discussions ghostwriter66 had with EVE engineers .... and she said that there were differences of opinion even among the EVE engineers about the best ways to compress the cells.
She said that according to the top engineer the recommended range to be maintained was between 14 and 22 PSI ..... The company she worked for installed LFP packs for various oil field application .... They bought so many cells that for a time period they had direct access to the EVE engineers and had hours of conversations with them.
I'd search for her posts in the 2020 time frame ..... I'll link a couple.
EVE-280 cells should these be clamped tight or spaced for expansion?
This is fun, I independently came up with the 12 PSI number based on the clamping force divided by the surface area of the large side of a cell: 661 lb / (8" x 7") = 11.81 PSI Is anybody looking at using Belleville Disc Spring Washers? They provide a very high spring rate for their size...
diysolarforum.com
EVE-280 cells should these be clamped tight or spaced for expansion?
I’m of the belief that the corners of a prismatic cell normally Keep their shape and any bulging comes from the large flat sides, the weakest point, which would probably be the center of the cell. By using a full spacer pad, any expansion will have A place of resistance. I chose not to use a...
diysolarforum.com
Search results for query: compression
diysolarforum.com
The concerns I have about foam is that in my experience it degrades over time ..... I realize that the Poron stuff has very good specifications for longevity, but I remain skeptical that it will maintain it's specified compression over time and temperature changes ...... I do, however, appreciate that placing foam between each cell might help reduce the stress on the bus bar connection points .... and once a good foam solution is arrived at, it would be easy to duplicate.
That the foam is not rigid would be at the bottom of my list of concerns about foam.
My favorite way to achieve and maintain compression would still be using rigid insulated spacers and rigid end plates with springs that will maintain the 14-22 psi range thru even with expansion and contraction of the cells ..... and use flexible bus bars.
I do, however, think snug is fine for most stationary applications and there are more important things to be concerned about when building a DIY pack.
Warpspeed
Solar Wizard
Have to agree.
EV applications are a bit different to ours, high heat, movement, vibration, in a moving vehicle.
Ours just sit there at ambient temperature.
I used the 1mm fiberglass sheets that are supplied with the cells purchased from Luyuan Technology (Amy Wan).
Made some super heavy 50mm thick wooden shelving to carry the weight without long term sagging, and full length 12mm threaded rods to hold it all together.
I did not use the supplied rigid cell links, but heavy duty stranded cable, and crimped lugs to prevent any stressing on the terminal posts.
Torqued up the threaded rods until the cells just refused to slide against each other and no more.
Its all super rigid and robust, but without applying extreme clamping pressure.
Pierrot
New Member
- Joined
- Apr 21, 2020
- Messages
- 27
they used paste silicon sheets instead...those are not manufactured battery packs. those are boxes made to fit a variety of cells for people to assemble themselves. no warranty, no risk. they just need the cells to fit. i actually addressed these exact style of boxes in an early comment.
BUT eel actually does have a video of another product, and it is a pre-assembled pack... ill let you guess if they used foam or not....
they dont
Zwy
Emperor Of Solar
Silicon rubber?
correct, as "insulation buffer", not anything to do with compression or expansion.
you can actually see the two VERY thin strips that are about an inch wide, and they put one on the left side and one on the right side, nothing in the center. then they put rigid end plates on and clamp it all together.
they are not using anything to damped the expansion and compression lol.
Not thrilled with Eva foam. 15 pounds on a 1 square inch area overnight and 2 hours of freedom and the resiliency is pretty poor. Eva is closed cell where real Poron is open cell. Closed cell sounds good until you realize that the bubbles have fractured. Open cell foam is dependent upon the material, not the trapped air. Going to repeat the same test on Poron when it comes in from EBay. Eva burns pretty easily(see corner). Burns like a nylon rope and smells like candle wax. 
