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CALB grey cell compression casing - these cells don't sit flat together.

BlitzSSS

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Hey all

I know the topic of cell compression has been discussed heaps and I'm looking into how best to do it for my situation, I was most likely going to use hose clamps at the top, bottom and middle of the cells with alloy C channel to locate the hose clamps and keep the cells really flat.

However one thing that concerns me is that these cells do not sit perfectly flat together and if I apply the middle hose clamp too tight I could actually be compressing the cells into a slight concave shape.

If I was to make something sit flat on the ends so this pressure is not applied in the middle, these cells still have these gaps running between. I have attached a picture.

Any advice on this please?

Thanks
 

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What SOC are they currently at? Its possible they will 'fill out' at a higher SOC.

The most common method of compression/fixture I have seen with plastic cells is clamping between two boards. Mostly I have seen this with the ribbed cells.

I believe (but cannot verify) that compression is less crucial (still recommended) with the plastic cells. Does the CALB datasheet give any guidance on this?

@HighTechLab may be the person to talk to about these cells, I believe he has done a good bit of research and has a decent bit of experience with them.
 
Hi, brand new cells probably only seen 1 maybe 2 cycles. They have been charged, up to 3.60v and have been rested down to 3.49v when I took that pic above.
 
Hi, brand new cells probably only seen 1 maybe 2 cycles. They have been charged, up to 3.60v and have been rested down to 3.49v when I took that pic above.

Interesting, so that is a picture of the cells at a full State of Charge. I did not expect that.
 
The compression recommendation is based primarily on the EVE cell specifications .... I don't know if the calb cells have similar requirements or not.
 
The compression recommendation is based primarily on the EVE cell specifications .... I don't know if the calb cells have similar requirements or not.

Agreed. EVE is the only manufacturer I've seen that specifically calls for a certain amount of force to be applied.

I do see, that this CALB user manual (attached below) does recommend 'clamping' the cells, but doesn't elaborate beyond that. What I have heard (word of mouth, not manufacturer specs/guidance) is that external compression and protection is more crucial with the aluminum cased cells (particularly the larger form factor cells).
 

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  • User+Manual.pdf
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Most of the Calb, SinoPoly, Winston installations (which all have similar ABS plastic casings) I have seen displayed, discussed or built have all been slightly compressed. The Marine How Tos from Nordkyn and the rest all indicate that. Compressed but NOT squished, just very firmly squuezed to prevent any movement and to eliminate expansion & contraction as that can stress the terminal points, as well, over time causes problems within the "jelly roll" inside.
 
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If you look at the cell mentioned above they have some sort of "ribbing" that possibly helps with structural support of the cell, unlike these newer smooth wall cells. Which I think that just getting them snug is good enough compared to what some new manufacturers require x amount of pressure.
06-LiFePO4-On-Boats.jpg
These are specific to GBS cells which holds the cells together but is not "compressed".
20200126_101503.jpg20200126_101527.jpg20200126_101600.jpg
The GBS battery above is from early this year at near 100% soc and over 1,400 partial cycles of 30-35% +/-. There is no deformity what so ever. The code if you notice on the side is 1507251049 which mean July 25, 2015 cell#1049, 50, 51, 52.
 
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Hey all

I know the topic of cell compression has been discussed heaps and I'm looking into how best to do it for my situation, I was most likely going to use hose clamps at the top, bottom and middle of the cells with alloy C channel to locate the hose clamps and keep the cells really flat.

However one thing that concerns me is that these cells do not sit perfectly flat together and if I apply the middle hose clamp too tight I could actually be compressing the cells into a slight concave shape.

If I was to make something sit flat on the ends so this pressure is not applied in the middle, these cells still have these gaps running between. I have attached a picture.

Any advice on this please?

Thanks
A late reply and partially mentioned in some responses but the gap shown appears due to a ridge on the cap preventing the cells being flat against each other. Its higher at the top, tapering to contact at the bottom.
 
If you look at the cell mentioned above they have some sort of "ribbing" that possibly helps with structural support of the cell, unlike these newer smooth wall cells. Which I think that just getting them snug is good enough compared to what some new manufacturers require x amount of pressure.
View attachment 23777
These are specific to GBS cells which holds the cells together but is not "compressed".
View attachment 23778View attachment 23779View attachment 23780
The GBS battery above is from early this year at near 100% soc and over 1,400 partial cycles of 30-35% +/-. There is no deformity what so ever. The code if you notice on the side is 1507251049 which mean July 25, 2015 cell#1049, 50, 51, 52.

Like many people on this forum I'm puzzled by the question "to compress or not compress"...
Many people suggest it's best to compress to 12 psi - which is a rather vague specification...
Perhaps my math is incorrect - but for me 12 psi translates to placing a 660 pound weight on the cells.
But is this 660 pounds per cell or for a stack of 4, 8, 16 cells?
I'm also unsure if the pack should be compressed to 12 psi?
Or should the 'fixture' be capable of withstanding 12 psi of outward force generated by the hydraulic force of cell expansion?
If it's the later - as I suspect - then each cell in the 'fixture' would generate 12 psi of outward force.
Therefore the combined outward force of 4 cells on the fixture would be something like 2,640 pounds.
Using end plates of 1/4" aluminum and threaded rod (tightened down 'firmly') seems like a reasonable compromise...

Screenshot 2020-12-29 at 4.30.09 PM.png

Last year I purchased a second GBS 60ah pack to increase my total capacity to 120ah.
This required dissembling each 12v pack and converting them to 6 volts packs to be wired in series for a total of 12 volts.
In other words - I wanted a 4s2p pack to accommodate my 4s BMS

Before doing this I contacted Elite Power and inquired if this was OK and how best to do it.
They emailed me the attached document "Cell Re-Arranging Instructions".
They describe using a 12 ton hydraulic floor press to compress the pack enough to get the end plates re-attached.
I didn't have a hydraulic floor press so I cobbled together a substitute.
Indeed - it required a lot of force to compress the pack enough to get the end plates screwed back in place.

IMG_20191115_202555 (1).jpg

IMG_20191121_173306 (1).jpg

For those who prefer the "duct tape & bailing wire" approach perhaps they should consider "Scotch® Filament Tape 8981"

Screenshot 2021-01-03 at 12.17.44 PM.png
 

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  • GBS battery pack compression Cell Re-Arranging Instructions (1).pdf
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