Pouch LiPo Pack Design - Compression Needed>

Hello,
I am building my power wall usingSPIM08HP cells. These are LiPo pouch cells. I have a pretty good idea on how I am going to construct the packs, however I can't see to get straight data on compression. Should the pouches have slight compression or have space in between? In the 75p14s configuration I am going to build them in, the load or charge current is not going to be high enough to even touch either charge/dischargeC rating. So, the question is, to compress or not?

Thanks

All pouch cells need compression, but good luck finding data on how much they need.

Have you purchased those cells allready ?

You know there'll likely have been removed from a much larger format battery, seeing as you require so many is buying the entire pack an option, you'll then have no issues regarding compression to contend with, and you'll likely get more storage for your money.

I have already bought the cells.

My plan is to have 25 in parallel in one pack. I was going to use a piece of acrylic on the ends of the pack as the main structure and then use threaded rod through the terminals, with washers in between the cell terminals, then tighten the 4 threaded rods with nuts/washers on the acrylic ends. The thread rod will end up being my bus bars for each pack this way. So should I just make sure the stacked washers + terminal thickness + 1-2mm taller then the cell? This way there is some compression, but more rigidity then anything else, while maintaining good contact on the terminals.

EDIT: Couple typos here and there, its late.

Wouldn't there be a risk of eg tearing the tabs if swelling did occur somewhere in the stack?
There would probably be a bit of fiddly adjustment as you tightened the stack up.
Would it be better to break into several smaller stacks?

Redpacket said:

Wouldn't there be a risk of eg tearing the tabs if swelling did occur somewhere in the stack?
There would probably be a bit of fiddly adjustment as you tightened the stack up.
Would it be better to break into several smaller stacks?

Click to expand...

I am not sure if the terminals would tear off.
The adjustment I am not too worried about, but I am sure I will run into things as I build.
I already have to make 42 of these 25p packs, so if I can avoid it, I would rather not make smaller packs.

Any prismatic pack needs compression but not as much as you would think. Expansion of a cell uncompressed can be as much as 30% it's thickness and the static compression should only be about finger tight plus 1 turn for standard threaded rod (fine thread) what you need is the ability to hold that distance under pressure. Plastic might not be strong enough as most of those are normally housed in a Metal case.