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Another Cell Compression Thread, this time about foam

Has anyone used foam and then polyimide tape
I just used polyimide on the cells then 3M VHB tape on top of the polyimide tape (only so that I can remove both of them more easily; VHB is hard to get off once it has set). I haven't implemented my cell-compression fixture yet but they are sitting there stuck together quite nicely, and I picked up 4 cells to lift them into my battery box and they stayed together with no slippage.
 
I'm jumping into this thread, because I have just disassembled a 12v battery pack, in use for about 3 years, and I have found that all 4 cells are significantly swollen after that time. It was a foam compressed battery pack; the foam was both very tight AND quite ineffective. The outer case was plastic, and maybe allowed some expansion of the outer case as well. When I set the cells down on a solid table and push them together, there is a gap of about 1/16 between adjacent cells. This gap appears in both of the side joints, and also along the top. It is due to cell expansion, with the largest "bulge" present in the middle of each cell face.

Although their total lifespan is significantly compromised already, these cells are still good. I have disassembled to replace a failed BMS, and I will be rebuilding it with compression springs. In this case, foam was unable to provide the hundreds of pounds of compression which the battery packs required. The cells are 6.5 inches tall and 7 inches wide, so I have calculated a force of about almost 300 lbs on those cell faces (6.5 * 7 * 6 PSI = 273 lbs), increasing as the cells become highly charged. Without steel rods and compression springs on two very solid end plates, it seems impossible to achieve.
 
Several questions, open cell or closed cell foam? Did you have specs for it? And I'm assuming the plastic enclosure was not a compression fixture?

This what my fixture looks like without cells and assembled with cells. Cells are in constant compression, it is not possible for the ends to move outward.
 

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It was closed cell foam, but the plastic enclosure was NOT in compression (lacking compression rods). It was bulging a bit, and did not have metal end plates. I see your diagram using solid aluminum sides to spread tension from the rods, that's almost exactly like the battery I'm in the process of building.
 
I didn't need that thick of plate, it was just what I had laying around. But it worked to my advantage, I was able to tap threads into the bottom to attach 2 angle on the inside to hold the lower plate off the rods. This allowed me clearance for a 200W heater strip. The lower plate length was determined by taking all the cells in line bare clamped lightly together with a couple bar clamps and measuring the length. I then took the 25mm for the 5 sheets of 5 mm foam that were used and multiplied it times 75% which came to 18.75 mm. Added that to the length of the bare cells, I believe the magic number was 308 mm but I'd have to double check.

I'm not certain if you have seen the final install where it currently resides. Note the pvc covers over the threaded rod. I did ream the pvc out slightly on the end to allow a flange nut to be installed in reverse, flat serrated end towards plate. A nut on each end, pvc was cut to 308mm and nuts were set to 308mm. This allows even compression in length both vertically and horizontally.

Another added bonus to the thicker plate was I tapped threads in the end plate to mount the BMS.
 

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All of these suggestions of different flammable foams seem confusing too me. Silicon nonflammable baking sheets just seem like the perfect nonconductive, corrosion resistant, cushioning as spacer/shock absorbers for between the cells.
 
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All of these suggestions of different flammable foams seem confusing too me. Silicon nonflammable baking sheets just seem like the perfect nonconductive, corrosion resistant, cushioning as spacer/shock absorbers for between the cells.
Give me the specs on those. :)
 
All of these suggestions of different flammable foams seem confusing too me. Silicon nonflammable baking sheets just seem like the perfect nonconductive, corrosion resistant, cushioning as spacer/shock absorbers for between the cells.

What I used meets the MVSS302 spec which is as follows and this is the current version.

 
I can also state for a fact a direct flame using a propane torch directly on the material is the only way it will burn but as soon as the flame is removed the material extinguishes the flame.

It's not as flammable as you might believe.
 
I can also state for a fact a direct flame using a propane torch directly on the material is the only way it will burn but as soon as the flame is removed the material extinguishes the flame.

It's not as flammable as you might believe.
Good to know.
 

How about encapsulate the cells in a battery box at a low SOC with 6lb stuff.
Dude, you just answered the question I needed answering. I am taking a 14K liter stainless tank (from a milk truck) and burying it with hot water heater elements on both ends.... (diversion tank for hot water and house heating). I was looking for an expanding foam for insulation in bulk as spray foam is not available where I am at. this stuff will be perfect to surround the tank with for insulation purposes. I can dig down, lay a concrete pad, and set the tank on it and then cap the ends with concrete for access but cover the bottom, sides and top with foam for insulation purposes thanks for the link.
 
Have you had any reason to disassemble your pack and check your foam? I'm curious whether the foam you used has taken much of a set. I came across this thread while researching PF100. I would much prefer to use appropriate foam and not have external springs.

Honestly, I wouldn't expect much set in closed-cell neoprene at 25% compression, but it would be nice to see real data. If you have some left over, perhaps you could run a test for us.
 
Have you had any reason to disassemble your pack and check your foam? I'm curious whether the foam you used has taken much of a set. I came across this thread while researching PF100. I would much prefer to use appropriate foam and not have external springs.

Honestly, I wouldn't expect much set in closed-cell neoprene at 25% compression, but it would be nice to see real data. If you have some left over, perhaps you could run a test for us.
I went to Poron now, I do have the one pack with the USA Sealing Foam in it but it would be a royal pain to take it back out and apart.

I'll look and see if I have some left over, I might be able to run some type of comparison to Poron once I get my house 48V system installed later this year. It would probably be a year before any results from that test.
 
I went to Poron now, I do have the one pack with the USA Sealing Foam in it but it would be a royal pain to take it back out and apart.

I'll look and see if I have some left over, I might be able to run some type of comparison to Poron once I get my house 48V system installed later this year. It would probably be a year before any results from that test.
Thanks. I did notice that even PF100 specifies the set only after a short period, and with some elevated temperature. The stuff still seems a bit hard to find, and it isn't nearly as cheap as other foams.

No time like the present to get started on a long-term test for the sake of science! LOL. Maybe put a measured area of it under some measured weight (books, perhaps) and measure the compression (by measuring the gap), then measure the gap every month. You could also then unstack it right after that monthly measurement and measure the pad thickness, then restack it. We would love to see the results.
 
I went to Poron now, I do have the one pack with the USA Sealing Foam in it but it would be a royal pain to take it back out and apart.

I'll look and see if I have some left over, I might be able to run some type of comparison to Poron once I get my house 48V system installed later this year. It would probably be a year before any results from that test.
Which Poron product do you use now in place of the USA Sealing Foam? It's a bit confusing to get the specifications listed at Grainger and McMaster-Carr to match Rogers Corporation material data sheets.
 
Maybe as insulation between cells. It’s my understanding that what you’re looking for is Neoprene that when place between the 30%SOC cells and compressed its COMPRESSED thickness @25% will provide approximately seven psi. Further when the batteries expand each approx .5mm, the resulting compression does not exceed 17 psi. Seems tricky but I’m getting samples through AliBaba and the price should be around $4-5 per pad. Need to test them with FORCE GAUGE!
 
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