john61ct wrote: ↑
May 14 2021 12:49am
Yes compression case is required for LFP pouch or prismatic.
The modules currently shipping include the inter cell frames - but not the big heavy casing for the whole pack.
I'll use the frames with studs and nuts with end plates for compression, then build a case to provide rigidity, space for the bms etc.
Are there any published or derived specs on the compression pressure - too much is probably as bad as none.
back on topic...I've come up with a copper welding method that can work for me, though it's probably more fiddling than most people want to do.
I fold the parallel nickel strip where it passes over the cell, so it creates a tab sticking up.
My copper series connector is .1 mm copper folded lengthwise, dropped over the nickel tab, then spot welded from opposite sides.
I do have to make an adjustment on the welder when I go from the nickel strip to the copper nickel sandwich, but I do get strong welds when I do so.
If I make any big packs, I'll need a second welder to avoid that hassle - and new leads - the ones included are short af as well as not ones where the electrodes can be replaced - probably more insulation than copper too.
If I make jigs to do the folds uniformly, it shouldn't add all that much time to assemble.
I can also probably get the added height down - right now, doing it freehand adds about 1/2" top and bottom.
My folded and welded copper bus is effectively 25mm - which is overkill.
Current on series path will only traverse about .2 mm of nickel per cell.
I still have to come up with a easy method to support the pack.
I could probably get by with just an insulation mat, but I don't like the idea of the pack bouncing along supported by the series rails.
I can probably do fins on the bottom of the case so the battery weight rides on those.