Thin insulation between swallen cells?

[cajocars]

I have been using my battery for almost a year with compression but with 2mm foam between cells (it's underfloor insulation, kind of polystirene).
Now I've separated the cells because I'm moving them into an unheated room and I need to put heating pads below each row.
Since the heating pads are just slighly longer than 8 cells, I wanted to reduce the spacing between them and bought some ready made 0.5mm epoxy sheets, but I have now realised that the cells have swallen a bit so they won't nicely touch each other around all surface as when they were new but only in the centre.

Is there any point in using these new thin spacers (on the right in the picture), or should I keep using the thicker (and softer) ones on the left?

 

[sunshine_eggo]

Any non-conducting spacer that doesn't damage the shrink is fine.

If the "swelling" you mentioned is what's evidenced at the right end of the pack, I wouldn't be concerned, particularly if you can close the gap with compression.

 

[cajocars]

Any non-conducting spacer that doesn't damage the shrink is fine.

If the "swelling" you mentioned is what's evidenced at the right end of the pack, I wouldn't be concerned, particularly if you can close the gap with compression.

Yes, the swelling is what you can see on the right, probably about 2-3mm
I don’t feel too confident in closing it by compressing the cells

 

[sunshine_eggo]

Yes, the swelling is what you can see on the right, probably about 2-3mm
I don’t feel too confident in closing it by compressing the cells

Using a board or other stiff end "plate," can you minimize the gap simply with firm hand pressure?

These cases have a fair amount of natural distortion. I've seen brand new cells at that gap.

 

[cajocars]

Using a board or other stiff end "plate," can you minimize the gap simply with firm hand pressure?

These cases have a fair amount of natural distortion. I've seen brand new cells at that gap.

No, I can’t. The cells were also at 75% (or rather the battery was) when I disassembled them, maybe I should discharge them first?

 

[sunshine_eggo]

No, I can’t. The cells were also at 75% (or rather the battery was) when I disassembled them, maybe I should discharge them first?

I think I'm missing your primary concern. You say you've been running them compressed. Do you intend to re-compress them?

 

[cajocars]

I think I'm missing your primary concern. You say you've been running them compressed. Do you intend to re-compress them?

Yes, I've been running them compressed, but there was a very soft material in between them (3mm polystyrene) which might have negated the actual compression, as I suspect it would still have allowed the cells to expand.

 

[sunshine_eggo]

Yes, I've been running them compressed, but there was a very soft material in between them (3mm polystyrene) which might have negated the actual compression, as I suspect it would still have allowed the cells to expand.

Ah. Mechanically speaking if you have 100# of force on the end, each interface experiences the same 100# of force, so it was still compressed, but the soft foam may have allowed the cell cases to expand into the foam width.

No worries. replace with the new spacers and re-compress.