I think you underestimate how rigid metals are. Say I wrap my battery in a 10mm steel box, similar to what EVE seem to be doing when welding. Having 250mm height and 130mm width I get 2 x 250 mm x 10 mm + 2 x130mm x 10 mm = 5000mm² + 2600mm² = 7600 mm² cross-section area.
Or, let's use aluminium instead of steel, since it's not even half as rigid at 69 GPa.
If we apply 50kN over 7600mm², that gives 6.579 MPa. That creates a stress of 6.679 MPa / 69 GPa = 0.0000967. Over the length of 8 of my 36.35mm cells, a total of 290.8 mm, that gives 0.0000967 * 290.8 mm = 0.02mm of elongation if I'm not messing up my calculations. Or, 0.0035mm per cell.
Using 6 M16 rods of 200GPa steel we get 6 * 125mm²= 750mm². Applying 50 kN we get 66.67 MPa. Stress = 66.67MPa / 200 GPa = .00033. Over 290.8 mm we get 0.097mm elongation. Or 0.012 mm per cell. We can continue calculating how much this would decrease the pressure, but I don't think it would be that much..
For the LF280K it doesn't seem to be necessary, no. I'm not sure whether you have LF280K or LF280 though.
Yeah, It's partly an exercise in welding too. Might be useful to learn.
Indeed. In my case I have the width of a 19" rack to work with, and I can't fit 16 cells from side to side, so it becomes 2 rows of 8 and thus have plenty of room for springs and bolts. I considered using LF280K and placing them from front to back instead, but 16 cells in a rack would become impossible to handle.
I might get sidetracked with other projects before adding this, but it seems like fairly easy data points to add to indicate a possibly severe issue with the battery. The cost of adding it is nothing compared to the cost of the possible consequences of an issue.
In my case I'm trying to add this to a lead UPS where much of the battery handling is a black box I have to work around.
In my case I don't trust the BMS fully, especially since it can't communicate with the UPS.
100 000 N, or 10 000 kgf. Looking at a data table this is within what two M12 (½") rods can hold before starting to deform permanently.