Lithium Cell Clamping -- Best Practice?

[Dockhead]

What is the thinking on best ways to clamp LP cells?


EVE provide a specification for clamping force, so clamping does not seem to be optional.


So what are people doing? Threaded rods with metal clamping plates? Silicon pads between the cells? Can you do 8 of them in one clamped pack, or do you need to split them up?


Grateful for any enlightenment, and hopefully will be useful for others also.

[fxykty]

Every manufacturer had different regarding the need for clamping or not so stick with what Eve is telling you. As a counter point, our Winston cells for example come with fixed-length steel straps that hold the two longitudinal aluminium clamping plates that when screwed into place provide minimal clamping force - they’re just there to hold the pack together. Winston provides straps for both 4 cell and 8 cell packs.

I’ve seen plenty of fancy threaded rod and plywood setups so that seems a common DIY solution to clamping cell packs. A simpler alternative would be to use ratchet straps, though you’d have to be careful to check their tension and retension as needed.

[Wandering1]

I use 1" chopping board for my 8s, 8 cell 280Ah batteries compression plates. To keep the battery square, I set them up in 2x bank of 4 but wired 8S.
6 lengths of 6mm threaded rod hold it all together.

[Dockhead]

Originally Posted by Wandering1

I use 1" chopping board for my 8s, 8 cell 280Ah batteries compression plates. To keep the battery square, I set them up in 2x bank of 4 but wired 8S.
6 lengths of 6mm threaded rod hold it all together.

Photos?

[PippaB]

I can only tell you what we get when the battery vendors (CATL, BYD, Lishen) assemble modules - a rigid box built for a tight fit. No clamping mechanism that pre-applies force, but so snug that any expansion of a cell results in considerable "clamping" force. Yes, it is a pain to get cells in and out if you need to. Possible, but not easy. If you do build it that way dimensions have to take into account the thickness of any cell separator. For lifting the first cell out, a pair of ring bolts that fit in the stud bosses make life tolerable.

[CaptainRivet]

Originally Posted by Dockhead

What is the thinking on best ways to clamp LP cells?


EVE provide a specification for clamping force, so clamping does not seem to be optional.


So what are people doing? Threaded rods with metal clamping plates? Silicon pads between the cells? Can you do 8 of them in one clamped pack, or do you need to split them up?


Grateful for any enlightenment, and hopefully will be useful for others also.

Till max 8 cells in a row you simply clamp them with 8mm rods. If you can do 4 in row in u-shape it's better as they expand less but 8 are ok too.
Important is even clamping so min 2 and better 3 per side, one on top additional is good too and also works well to use as cable guide for balancing cables.

[newhaul]

My cells are aluminum cased and there was no requirement for compression beyond sufficient to keep cells contained so they don't move around.
Here's my solution. It has worked great for 5 years now but I'm open to changes if it will get a better long-term result.
I used micarta strips for minor separation for cooling of each cell

[CaptainRivet]

Originally Posted by newhaul

My cells are aluminum cased and there was no requirement for compression beyond sufficient to keep cells contained so they don't move around.
Here's my solution. It has worked great for 5 years now but I'm open to changes if it will get a better long-term result.
I used micarta strips for minor separation for cooling of each cell

All these aluminum case prismatic cells need proper compression for significant more cycle life.
The clamping need to be evenly on the full surface of the cells. Important is especially the middle of the cell.
Your "clamping" is the worst as moving around prevention as well as technical clamping.
The case carries positiv so it's advisable to take as clamping plate non conductive material or at least and non conductive sheet inbetween. And the case/clamping is also physical protection for the cells.

[newhaul]

Originally Posted by CaptainRivet

.
The case carries positiv so it's advisable to take as clamping plate non conductive material or at least and non conductive sheet inbetween. And the case/clamping is also physical protection for the cells.

Not correct with properly manufactured cells there is no charge to the case . None nada zero zilch. does not happen .
Go back and look at a couple of my various refit/ build threads where I answer all of your questions about my cells and how and why of it all.

And yes I do recall answering several questions from a guy that was looking for specific information.

[CaptainRivet]

Originally Posted by newhaul

Not correct with properly manufactured cells there is no charge to the case . None nada zero zilch. does not happen .
Go back and look at a couple of my various refit/ build threads where I answer all of your questions about my cells and how and why of it all.

And yes I do recall answering several questions from a guy that was looking for specific information.

You have EVE cells?

[newhaul]

Originally Posted by CaptainRivet

You have EVE cells?

CATL cells
now
Go back and look at my defender refit page start with page 7 on the thread. For my lifepo4 stuff.
Do some background like I suggested it would save us both some time and me some bandwidth.
https://www.cruisersforum.com/forums...7&d=1578732330

https://www.cruisersforum.com/forums...-187721-7.html

[wholybee]

The clamping is only meant to prevent any distortion or swelling of the cells as they go through charge/discharge cycles. You will see several numbers given for what the force is. The bottom line is this. You want to clamp them with enough force that they can't move, and can't swell. But not so much that you distort or compress the case of the cell.
I used 4 threaded rods and 2 pieces of plywood. You should put some sort of insulating material between the cells. Thin HDPE sheets work, I've used those sold a the grocery store as flexible cutting boards.

[CaptainRivet]

Originally Posted by newhaul

CATL cells
now
Go back and look at my defender refit page start with page 7 on the thread. For my lifepo4 stuff.
Do some background like I suggested it would save us both some time and me some bandwidth.
https://www.cruisersforum.com/forums...7&d=1578732330

https://www.cruisersforum.com/forums...-187721-7.html

Well chosen, the good CATL with 2C.
CATL also need compression of 300kgF +/-20 equivalent to the EVE and also Lishen
Also the alu case is most likely positive under the heat shrink, the same as EVE and Lishen. Cannot find data for that cell but typically the case is positive with all alucase prismatic cells. On older datasheets you often don't find the compression data as they all found out later prismatic cells need compression. Was also not EVEs first sheets but they where the first to put it on.

Here is a comparison of the 280AH cells which shows on the datasheet also the compression rate. The 280AH cells are the bigger version of yours but technical identical, just less capacity.
https://lythbattery.com/280ah-lifepo...ishen-vs-rept/

I use for the m8 rods 5nm and let it settle and then retighten with 7nm after the first week when cells run in. That gives a clamping force around the 300-350kpF in tests a buddy of mine done at Swiss EMPA. Worked well over the last 7 years.

[newhaul]

Originally Posted by CaptainRivet

Well chosen, the good CATL with 2C.
CATL also need compression of 300kgF +/-20 equivalent to the EVE and also Lishen
Also the alu case is most likely positive under the heat shrink, the same as EVE and Lishen. Cannot find data for that cell but typically the case is positive with all alucase prismatic cells. On older datasheets you often don't find the compression data as they all found out later prismatic cells need compression. Was also not EVEs first sheets but they where the first to put it on.

Here is a comparison of the 280AH cells which shows on the datasheet also the compression rate. The 280AH cells are the bigger version of yours but technical identical, just less capacity.
https://lythbattery.com/280ah-lifepo...ishen-vs-rept/

I use for the m8 rods 5nm and let it settle and then retighten with 7nm after the first week when cells run in. That gives a clamping force around the 300-350kpF in tests a buddy of mine done at Swiss EMPA. Worked well over the last 7 years.

I was told no compression necessary. By CATL technicians. Also no charge on the cases personally tested with my fluke. Was a concern raised on w thread concerning differences of aluminum case and plastic. So I tested my cells and no stra6 current positive or negative on my cell cases which leads one to believe superior construction at the contacts points where they penetrate the cases.
Here is a shot of mine when I took delivery several years ago.
Yes I like the CATL construction

[CaptainRivet]

Originally Posted by newhaul

I was told no compression necessary. By CATL technicians. Also no charge on the cases personally tested with my fluke. Was a concern raised on w thread concerning differences of aluminum case and plastic. So I tested my cells and no stra6 current positive or negative on my cell cases which leads one to believe superior construction at the contacts points where they penetrate the cases.
Here is a shot of mine when I took delivery several years ago.
Yes I like the CATL construction

I like them too.

Ask now again, several years ago they didn't know about compression but now all state clamping. Was the same with my Lishen. All prismatic aluminum cell needs it.
Build a proper case and clamp them on the full surface to also protect them from external damage. Cannot hurt, in worst case it has no impact but in best case can significantly improve lifespan (>25%)
The way you "clamp" them with space inbetween is the worst way as I wrote above.