Gosh darn it now you make me want to evaluate a 280/310Ah cell free standing with interval photogrammetric reconstruction of cell face geometry. Spray paint can create speckle pattern that allow very easy reconstruction with even cell phone camera.I wish I had access to some of the high resolution 3D scanners I had before the pandemic started. Take one of those to the side of an EVE cell and you’ll see that the “flat” sides are really very hilly when you look microscopically.
When discharged, the highest ridges are probably at the edges of the cell, meaning the center is concave-ish. When charged, you’ll have the characteristic swelling of a lithium cell.
clamp a cell between two hard, flat surfaces, ok - *maybe* you can get a reasonable pressure distribution that way. Definitely not as consistent as you could with a compression pad.
but clamp multiple cells together under that same 11 psi and you have a very different pressure profile between cells - one that imparts high pressure (>11 psi) at the cell edges when discharged and high pressure at the center when charged (again, larger than the 11psi design value).
adding a pad between cells with the right composition can ensure that you have that 11psi of pressure across the entire face of the cell.
Or print out perlin noise:
And affix it with adhesive or double sided tape to cell wall.
Go through a charge + discharge cycle. No compression, no enclosure. Single cell.
Every ~30 Ah (~10% SOC) increment, take photos of cell from different angles (4-12 angles should be enough.)
Process each set of ~10 images into a 3D model of the cell face for each state of charge. This could be very valuable data for community.
Wow I don't have time to do this but it would be fun!
Instead got 100Ah Frey cells and am only constraining the cells, not compressing the aluminum shell face.