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Compress or not, flexible busbar or not

Bonjour à tous..
un vendeur chinois m'a répondu à propos de la charge de compression de ses ressorts marron.
voici le tableauIMG_20221201_104958.jpg
 
1pc Spring, 634.6 LB @ .56" deflection
from MSC (mscdirect.com) PN 07661879. In the picture you can just see the spring and how much one fixture’s movable end plate moved after a full charge. (Approximately 3/16” for 8cells) I set the spring Initially 1/2” deflection for about 550lbs. DCD195E6-3E55-4965-8B8F-0E9B1447606F.jpeg
 
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I'm in the UK and have two rows of 8 EVE cells I'd like to compress, but when it comes to following the maths in this thread, and spring rates etc I'm completely lost.

Has anybody done spring compression on 8 EVE LF280K cells that would like to share their spring details please?
 
Hello,
6 springs diameter 8-16 brown (heavy load) in 50mm correspond to 600kgf
 
oui 8 intérieur et 16 extérieur en longueur 50mm (voir tableau précédent)
c'est-à-dire deux rangées de 8 cellules = 2x300kgf=600kgf=6 ressorts bruns
 
Ron-ski said:
I'm in the UK and have two rows of 8 EVE cells I'd like to compress, but when it comes to following the maths in this thread, and spring rates etc I'm completely lost.

Has anybody done spring compression on 8 EVE LF280K cells that would like to share their spring details please?
Click to expand...
Ron- read back through this thread and rest assured there is lots of info you ask
 
@1234enough I've read the entire thread, there was lots of bickering, arguing, lots of different opinions, and far too much info which I often didn't understand (or able to put into practice), and therefore my old brain gave up. Although that said it did help come to the opinion that I ideally need spring compression.

PS I've oredered the six springs that @oliagri suggested, the fabrication side I can handle no problem.
 
Ron-ski said:
@1234enough I've read the entire thread, there was lots of bickering, arguing, lots of different opinions, and far too much info which I often didn't understand (or able to put into practice), and therefore my old brain gave up. Although that said it did help come to the opinion that I ideally need spring compression.

PS I've oredered the six springs that @oliagri suggested, the fabrication side I can handle no problem.
Click to expand...
You can look back thru to see the red springs I used. I didn’t even compress the springs to 600lbs. The rig was very tight way before the full inch needed to achieve 600lbs. My springs compress maybe a 1/16 of an inch from 30% SOC to 99% SOC. Barely any measurable expansion and like I said I only compressed my springs 3/4” of the full inch i was supposed to do..
that kinda tells me compression isn’t needed as much as I originally thought if the cells are in good condition. but still a good idea to compress them for many other reasons discussed throughout this thread
 
Ron-ski said:
@oliagri I see, so six on one end like the attached but with suitable plates and rods, thank you.

Did you order via their website https://www.minglispring.com/product/mold-spring/tb-brown-standard-die-springs.html ?
Click to expand...
I got this quiz wrong in another thread. The force on the middle two springs should be twice as much as the outer springs, or 165#/330#/165#. This is shown in "D" below (sketch provided by user KYSolar).

1641305069735-png.78280
 
justgary said:
Je me suis trompé sur ce quiz dans un autre fil. La force exercée sur les deux ressorts du milieu doit être deux fois supérieure à celle des ressorts extérieurs, soit 165#/330#/165#. Ceci est illustré en "D" ci-dessous (schéma fourni par l'utilisateur KYSolar).

1641305069735-png.78280
Click to expand...
Bonjour
si vous utilisez un mur rigide vous pouvez appliquer la même force sur chaque ressort, le but est d'avoir 600kgf?
 
Skypower said:
1pc Spring, 634.6 LB @ .56" deflection
from MSC (mscdirect.com) PN 07661879. In the picture you can just see the spring and how much one fixture’s movable end plate moved after a full charge. (Approximately 3/16” for 8cells) I set the spring Initially 1/2” deflection for about 550lbs. View attachment 122522
Click to expand...
How many cells to move 4,7mm ??
 
oliagri said:
Bonjour
si vous utilisez un mur rigide vous pouvez appliquer la même force sur chaque ressort, le but est d'avoir 600kgf?
Click to expand...
I agree, but you show plywood in your build, not a rigid wall. Adjusting the forces as shown in "D" above gives you 600 kgf and balances the force so your "rigid wall" doesn't bend or place unequal force on your cells.
 
The rigid wall is something that I still haven't decided on. The straightforward option is with plywood. But this is not very rigid and is expected to sag with time.

So I'm thinking of aluminum or steel. Steel is thinner to get the job done. Aluminum will not rust. I'm kind of leaning toward aluminum. But there are a lot of types of it. 7075, 2017А, 6082? And what thickness?
 
I've ordered some 200mm wide by 10mm thick aluminium, no idea what grade, I doubt it will matter. Website just state's the following.
All of our aluminium is 6000 series material, the vast majority of which is produced in the UK to 6063T6. We also keep significant stocks of 6060 and 6082, all produced to comply with the exacting standards set out in BSEN755.
Click to expand...

I might make a solid enclosure, so have also ordered some 12.7 x 3.2 aluminium tube, the middle will tap to M8 and it could be bolted together to make a solid frame, same fashion as the Seplos 280 battery box - shame I can't get the exact dimensions and materials used in that.
 
1234enough said:
This is my now complete 18S eve280k battery, compressed with 6x threaded rods with nylon sleeve/ 18x 32x20mm springs - 3x on each rod / 20mm HD form each end, currently total approx 300kgf to allow it to settle, after a week will up compression to around 400kgf this will allow for expansion in the region of 12mm before compression goes over the recommended kgf.View attachment 119195
Click to expand...
Trully inspiring!
Thanks for the photo!
Could you please post a couple more pics?
Thanks in advance!
 
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1234enough said:
This is my now complete 18S eve280k battery, compressed with 6x threaded rods with nylon sleeve/ 18x 32x20mm springs - 3x on each rod / 20mm HD form each end, currently total approx 300kgf to allow it to settle, after a week will up compression to around 400kgf this will allow for expansion in the region of 12mm before compression goes over the recommended kgf.View attachment 119195
Click to expand...
hello! nice looking box.

may i ask what influenced the decision to go with 18S LFP? i am curious and wish to learn about the engineering factors that went into that aspect.

thank you for posting! love the cell interconnect, and nice work routing the sense/balance wires. love the flat flex cable.

is that a MEGA fuse? at 18S voltage, my understanding is that it may arc and fail to interrupt the circuit in the case of a short.

diysolarforum.com

MRBF or class T

MRBF vs Class-T fuse, i am also still grappling with this topic for LiFePO4 battery build. the tentative conclusion for me is, 12V LFP? MRBF probably ok. 24V LFP? MRBF *maybe ok* 48V LFP? Class-T Definitely the different cost in components is very important to me. class-t are generally...
diysolarforum.com diysolarforum.com

kind regards! ??️
 
7075 has the highest tensile strength. I'll go with 6mm plates. If the cells manage to bend it then it is probably time for new cells. Or at least this is the impression I'm getting after going over the full thread.
 
2 rows of 8 cells. Common plate on the sides. 2 rods on each side, 5 rods in the middle. All with springs. Below is the initial idea. Much or less the same as the Seplso Mason cases, but from plywood and with springs.
 

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