?I'm fixated in kicking myself...... for waiting to buy.
now they are sold out!
?I'm fixated in kicking myself...... for waiting to buy.
now they are sold out!
I missed this post.... “constrained “ is a much better term... but still needs to be expanded on..Manufacturers spec sheets I read say the cells should be "constrained" ... didn't say compressed. I gave up argueing with folks about it a couple of years ago when I started seeing all the rediculous spring contraptions people came up with.
How are your cells set up so that every cell gets the same amount of compression?Point me to the evidence.
I never have swelled cells, I always use compression. Side benefits of compression- no terminal stress, no creep on busbars which could cause a loose connection, no shifting of cells, cells remain close in temp to each other. There are more but those just come to mind quickly.
As for cell life, yes, I believe proper compression will extend lifespan/cycle life.
This is another layer of discussion...How are your cells set up so that every cell gets the same amount of compression
Simple..How are your cells set up so that every cell gets the same amount of compression?
... and if doing a simple spring type compression from the ends, most common would probably be 2rows of 8cells, how evenly is that pressure going to be distributed along the entire row of cells? These cells move quite a bit between 100% & 20% soc. I'd wager that simply applying the desired amount of spring tension at both ends of the row, does not equal the correct pressure amongst all the cells in that row. IMO, YMMV, $.02This is another layer of discussion...
cells are constrained( thanks @Q-Dog ) ... but mostly only along one axis....?
So the big question being how do we know if our cells were compressed initially to help squeeze out the “ bubbles “ before they were sold or distributed... ?... and if doing a simple spring type compression from the ends, most common would probably be 2rows of 8cells, how evenly is that pressure going to be distributed along the entire row of cells? These cells move quite a bit between 100% & 20% soc. I'd wager that simply applying the desired amount of spring tension at both ends of the row, does not equal the correct pressure amongst all the cells in that row. IMO, YMMV, $.02
Then there's this ... 7:15 if you like to ff
I know people use them outside a fixture - I wouldn't. All my cells are in a fixture (i.e. compression, but that's a wrong term really, gives people the idea they need to torque the thing down like crazy). Fixture: nuts hand tight. I've recently rebuilt my pack since I changed enclosure. This is a cell after almost 4 years, in use 24/7, sitting at 100% state of charge over summer and cycled, and sitting at low state of charge most of winter:
I'm fixated in kicking myself...... for waiting to buy.
now they are sold out!
Start here: https://diysolarforum.com/search/1928944/?q=compression+fixture&c[users]=Zwy&o=relevanceHow are your cells set up so that every cell gets the same amount of compression?
Yeah, nice search results. If using a 'spring loaded' jig, has anyone calculated that a 304ah Eve weights over 12lbs. x 8pcs resulting in around 100lbs of cells that have to slide back and forth as the cells expand and contract? Even worse if using 16 per row. How has the floor of the compression jig been treated to accommodate for the cell's bottom having to walk back and forth? Sure, the outer few cells may have correct, or close to correct compression, but it's doubtful the inner cells will see those same numbers.
Yeah, nice search results. If using a 'spring loaded' jig, has anyone calculated that a 304ah Eve weights over 12lbs. x 8pcs resulting in around 100lbs of cells that have to slide back and forth as the cells expand and contract? Even worse if using 16 per row. How has the floor of the compression jig been treated to accommodate for the cell's bottom having to walk back and forth? Sure, the outer few cells may have correct, or close to correct compression, but it's doubtful the inner cells will see those same numbers.
If it is a solid constraint, at what soc will the compression be correct, and for how many of the cells?
I'm not getting into that argument. One time someone posted a link to one of Andy's videos about cell capacity loss (trying to prove compression isn't needed) and I made the comment I wonder what capacity he would have lost if instead he had used cell compression in an actual side by side comparison. He never used an actual control group with side by side test so I considered the video just clickbait for views and nothing valid contained within.To compress, or not to compress, the cells are going to age out before they cycle out.
Are you stating that LiFePo4 prismatic cells do not exp[and and contract in relation to their state of charge?You must think cells really move around/expand when charged/discharged under compression.
No.Are you stating that LiFePo4 prismatic cells do not exp[and and contract in relation to their state of charge?
Do you have the data sheet, or other information on the expansion/contraction of prismatic LiFePo4 cells?
Here is one data sheet for example of the EVE 280K V3. https://diysolarforum.com/resources/eve-lf280k-v3-pbri-lf280k-d06-01-datasheet.376/Do you have the data sheet, or other information on the expansion/contraction of prismatic LiFePo4 cells?