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Best way to compress cells in packs

In doing my 16s4p setup, I ended up using 5/16” aluminum plating with 1/4” rods between every pack of four, 10-rods per 16s. (See photos) I used rubber matting in the inside of the aluminum where the cells contact. Originally was using rubber matting between each cell, but that was to thick for my racking & resorted to thin plastic between cells as cell separators.
After charging to full capacity and arranging the packs in the cabinet on the rack. I used 8 inch lbs of compression at roughly 98-99% SOC. It seems the swell variation is around 1-mm or less and that’s mostly in the battery center or middle.
I may adjust my torque once I see how much compression varies once they’re cycled several times and charged back to my 80% target.
My holes were drilled, one @ 2.5” and the second @ 6” from the bottom of the aluminum plates. Attempting to keep compression evenly spaced so not to compress the edges too much. So knowing that I’ll be charging/discharging my batteries at around .33C rates and in the 80% to 20% range, I felt this was good enough from what I’ve read and researched on the forums. Many options & opinions!!!
 

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Have you read thru the spring compression thread for ideas?


... or this one about using a special foam>
Yes, I read over these. I don't like foam because I concerned with how it may change over time. Springs look interesting but not sure what springs to get for EVE 280ah cells. Also what ever method I use I'm concerned with cell expanding and contracting putting force on terminals that why I'm considering 1AWG with lugs. What's your thoughts
 
Yes, I read over these. I don't like foam because I concerned with how it may change over time. Springs look interesting but not sure what springs to get for EVE 280ah cells. Also what ever method I use I'm concerned with cell expanding and contracting putting force on terminals that why I'm considering 1AWG with lugs. What's your thoughts
I looked into these springs but never went that route.

 
Yes, I read over these. I don't like foam because I concerned with how it may change over time. Springs look interesting but not sure what springs to get for EVE 280ah cells. Also what ever method I use I'm concerned with cell expanding and contracting putting force on terminals that why I'm considering 1AWG with lugs. What's your thoughts
If you look at my picture, you could use wire with lugs instead of buss bars to help with terminal stress. I didn’t do that but considering possibly changing only this buss bars. Only the ones with yellow highlights in my picture.
FC52B845-1F86-419D-8965-15A4A880AC1D.jpeg
 
yes, that what I was thinking.. I'm thinking for 280ah cells that 1AWG wire should do. Do I have my calculations correct?
 
Yes, I read over these. I don't like foam because I concerned with how it may change over time. Springs look interesting but not sure what springs to get for EVE 280ah cells. Also what ever method I use I'm concerned with cell expanding and contracting putting force on terminals that why I'm considering 1AWG with lugs. What's your thoughts
If that is sufficient for the current you will be using, that should work fine.

I think Upnorthandpersonal has the best idea for using braided bus bars to keep stress of the terminal. It's on my list to make up some but haven't gotten around to it yet.

Some of the builds on that spring thread show exactly what springs they are using.
 
This video is a good watch I think, for the compression question. Let me know what you think.

Wow, that video is fantastic.

The part around 15-16 minutes in where they use a flat DIN rail to show the curvature of the "flat" cell wall was quite interesting.

Jelly roll geometry squash science.

1632013591923.png
 
Thanks again, I realized that I can pick these up in exact quantity that I required! I did noticed that they are rated at 124 lb-in. I was thinking that for the EVE 280ah cells that one would want 165 lb-in for 4 rods???
Honestly I don’t know exactly that correct spring rate for this application. I was looking at the lighter weight springs because I wasn’t sure that I could compress higher rated springs with the limited rod length I was restricted to in my setup.
If you know a formulation for figuring the spring rate you need, trust that.
I was only looking for lite compression. I was afraid the higher rated springs I wouldn’t be able to compress onto my rods as my work area was limited for my to reach into. One reason I passed on springs all together.
 
Thanks again, I realized that I can pick these up in exact quantity that I required! I did noticed that they are rated at 124 lb-in. I was thinking that for the EVE 280ah cells that one would want 165 lb-in for 4 rods???
If you search the grainier website, they have tons of various length/strength/size springs.
 
I've attached the spec sheet for the Eve 280ah batteries. It gives the compression specs for their cells. The video I posted earlier from off-grid garage explains the spec.
 

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