Spring compression at full travel swelled cells

[Gurusi]

Hey, as above my compression pack is almost at full travel on the springs due to some pack swelling (see post for details https://diysolarforum.com/threads/bulges-on-side-of-cells-during-top-balance.69878/#post-883917 )

It is 16s 280ah x2 rows of 8 cells with a six spring formation. The two swollen cells are nearest the springs, one on each row.

Reading lots of posts on swelling bulging, advice is not to release compression. However due to the springs being at full travel I don’t want to put the other cells at increased risk or over pressure when the pack is in use.

Since the swelling I have discharged the pack to 3.35v however the compression remains at full spring travel. I will post the spring compression rating if that helps.

Any advice would be appreciated. I was considering testing some loads and reducing some compression at a lower SOC

 

[hwy17]

Automotive packs use rigid compression. But I don't have the experience to actually advise anything here.

This is the second post recently where people have reported swelling primarily on the end cells of the pack. I wonder if anyone has any thoughts on the mechanism there. I thought in a series string resistance anywhere in the circuit should affect the entire circuit equally. Could it be heat in the end terminal connections?

 

[Gurusi]

Automotive packs use rigid compression. But I don't have the experience to actually advise anything here.

This is the second post recently where people have reported swelling primarily on the end cells of the pack. I wonder if anyone has any thoughts on the mechanism there. I thought in a series string resistance anywhere in the circuit should affect the entire circuit equally. Could it be heat in the end terminal connections?

The end cells were definitely warmer and this was the point of + and - connection from the charger. They were connected in parallel for top balance purposes though.

Hoping someone can advise on the best course as looking to work on these today

 

[hwy17]

Ah I see. These events are happening in balancing. Still if positive is on one end and negative the other, it seems like current should balance. Idk. Look forward to hearing the theories.

 

[Gurusi]

Started rebuilding in series’s and cell 16’s flexible bus bar is full stretch. Not sure there is room to uncompress the pack.

 

[Gurusi]

Issue is now mute due to needing to remove all compression. Future post coming requesting assessment of bloatedness usability on individual cells…

 

[Nobodybusiness]

Started rebuilding in series’s and cell 16’s flexible bus bar is full stretch. Not sure there is room to uncompress the pack.

I have never seen mine swell that much. Just an FYi.

 

[Gurusi]

I have never seen mine swell that much. Just an FYi.

See the full horror here:-

Bulges on side of cells during top balance

Hey, just in the process of a 16S. 280ah top balance. Using the ZKEEBCA 40 L. They are Configured in parallel and a under compression. I had previously been using the cells with the inverters but found imbalance at the higher range of 3.4v when charging via the charge controllers I noticed a...

diysolarforum.com

Looking for opinion on their usability (which looks unlikely for some cells)

 

[Nobodybusiness]

See the full horror here:-

Bulges on side of cells during top balance

Hey, just in the process of a 16S. 280ah top balance. Using the ZKEEBCA 40 L. They are Configured in parallel and a under compression. I had previously been using the cells with the inverters but found imbalance at the higher range of 3.4v when charging via the charge controllers I noticed a...

diysolarforum.com

Looking for opinion on their usability (which looks unlikely for some cells)

Wow.
Never seen anything like that.

As far as usability I guess as long as they produce rated capacity they are fine.

 

[paircycle]

The internal resistance opposes the flow of ions. As the temperature increases, moves faster and more current is produced. This lead to decrease in the internal resistance.
If the outer cells are slightly cooler and therefore have a higher internal resistance, but the same current is still flowing, they generate more heat loss and degradation is faster?