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What is the easiest way to compress prismatic Cells?

unseengundam

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Hello,

I am thinking about would be the easiest way to compress 16S (~300ah) cells?

Seems like everyone is using thread rods and springs. Is that easiest to apply compression to keep the battery cells from moving?

Any other simple solution instead of having to build a compression structure with threaded rods + springs?

Thanks
 
Some people just wrap them in groups of four with tape. There are some types of tape that don’t stretch under pressure. Personally I do not prescribe to putting them under spring tension or force. What you want is to wrap them tightly when they are discharged so that they cannot bulge when charged.
 
I put some drawer liner material between mine and used small bar clamps to compress. I taped them with fiber tape in pairs then groups of 4 so the only compression is what the tape and the drawer liner provide. I also plan to use flexible copper busbars.
 
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Compared to the price of the cells, threaded rods and springs are cheap. I chose to put mine in a compression fixture to meet the recommendations of my cell manufacturer (EVE) for longest life. I also have flexible bus bars in order to minimize stress on my terminals.

ON EDIT: I should add that my application is mobile. If my batteries were to be static, I might contemplate something different.
 
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I wrapped in groups of 4. First wrap with 1 inch fiberglass filament tape, followed by a wrap of Polymide high temperature tape. I staggered the wraps to compensate for the stacks of 4 being joined together. I've had no problems at all.
 

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Some people have been using Puron foam .... a search should find that. I haven't seen any real testing with that setup to prove what it takes to make it work, however.
 
Some people have been using Puron foam .... a search should find that. I haven't seen any real testing with that setup to prove what it takes to make it work, however.
Rogers Corporation makes a type of Poron foam called EVExtend (tm). It is specifically designed for this purpose. It is proving difficult to source, however. I am not sure if anyone on this forum has acquired the correct foam and reviewed it, as yet.
 
I wrapped in groups of 4. First wrap with 1 inch fiberglass filament tape, followed by a wrap of Polymide high temperature tape. I staggered the wraps to compensate for the stacks of 4 being joined together. I've had no problems at all.
Hey Brett,

I love your enclosure! Did you just pick them up from a hardware store and what are the dimensions?

I am thinking about whether I can also put in 16S in such an enclosure.
 
Hey Brett,

I love your enclosure! Did you just pick them up from a hardware store and what are the dimensions?

I am thinking about whether I can also put in 16S in such an enclosure.
That's a truck toolbox I picked up on Amazon. Amazon 39" Toolbox For the 16 EVE 230's I have in there with the Overkill BMS, it's tight but I made it work. I bought another batch of 16 cells and had planned to build an identical battery enclosure but decided to get a larger toolbox that will hold all 32 cells. Amazon 48" Toolbox
 
I chose to put mine in a compression fixture to meet the recommendations of my cell manufacturer (EVE) for longest life. I also have flexible bus bars in order to minimize stress on my terminals.
What are the recommendations of the manufacturer? Specifications are hard to find using search functions.
 
That's a truck toolbox I picked up on Amazon. Amazon 39" Toolbox For the 16 EVE 230's I have in there with the Overkill BMS, it's tight but I made it work. I bought another batch of 16 cells and had planned to build an identical battery enclosure but decided to get a larger toolbox that will hold all 32 cells. Amazon 48" Toolbox
Great Brett V! I am definitely going to look into that in the future, looks like a nice enclosure!
 
IMSO. The 300Kgf equals about 662 Pounds-force. That indicates the side "compression plates" or what ever is used must prevent that much expansion force. The pressure is not applied to the battery, it is resisting the battery expansion while charging. my understanding is tape and springs and other such is not sufficient. What would meet 'specifications' is 1/4 inch aluminum plate on each end of the battery (the side of the cell), held with threaded rod and locking nuts such as Ny-Lok.
 
Hello,

I am thinking about would be the easiest way to compress 16S (~300ah) cells?

Seems like everyone is using thread rods and springs. Is that easiest to apply compression to keep the battery cells from moving?

Any other simple solution instead of having to build a compression structure with threaded rods + springs?

Thanks
Read this first. https://www.strouse.com/blog/types-of-poron-foam
 
Rogers Corporation makes a type of Poron foam called EVExtend (tm). It is specifically designed for this purpose. It is proving difficult to source, however. I am not sure if anyone on this forum has acquired the correct foam and reviewed it, as yet.
McMaster.com has the proper foam. https://www.mcmaster.com/86375K134/
The spring rate is around 11 psi however it's a bit pricey.

In my mind, there has to be some compliance in the fixture holding the cells together, or there is a risk of over pressuring the case,
And one thing I haven't been able to nail down is the expected growth range of a cell during a charge cycle. I arbitrarily selected 1.1mm per as a start.

I plan to use 4 springs per stack only because I know the characteristics and they're adjustable. I whipped up a little spreadsheet to help select the proper ones based on cell & stack assumptions. Several companies sell die springs that offer a wide range of rates & lengths to choose from.


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I'm guessing duct tape isn't a viable option? Or am I going to need to track down some VHD tape?
Depending on your expectations. Every spec I've seen says to cycle them under 300kgf +/- 20kg on the wide face.

Duct tape would provide zero pressure on that face.
 
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