This is my attempt at designing a battery made from A123 20ah pouch cells. This is basically just an evolution of Jack Rickard’s (EVTV.me) 2nd design which he demonstrated on his Dec 30th 2011 show. I thought that design was good, but that some space was going to waste.
So here’s my design so far:
- Light grey = A123 cell foil.
- red = positive cell tab.
- blue = negative cell tab.
- dark grey = 1/4 inch thick aluminium.
- pink/purple = screws / nordlock washers / nutserts.
- light green = cast urethane with a 2 nutsert in.
- medium green = cast urathane with 2 drilled holes for the screw and 2 big counter sunk holes for the screw end and nordlock washer.
- Dark green = cast urathane with hole drilled through it. Just there to make sure nothing slides around and to add a bit more insulation.
So the idea with this design is to save space to the point where you can just stack cells up against each other. Instead of having big square blocks of urethane and high molecular weight polyethylene I’m instead using “U” shaped blocks. I figured it would be simpler to just use one material, so I’m opting to just go with the urethane. One “U” shaped piece contains a nutsert and the other has a hole for the screws as well as a counter sunk hole to accommodate the screw head and nordlock washer.
If anyone ever actually makes this then they can play with the dimensions. In this design there is always a cells width (7.25mm) of urethane between any of the conductive metal pieces. The U shaped pieces are half a cells width at their narrowest point and 2 cells wide at their widest point.
I’m assuming it’s possible to generate enough clamping force with this design, but of course I may be wrong. If the urethane isn’t strong enough then you could either thicken it or cast a piece of aluminium with 2 holes for the screws in with the urethane.
This is a work in progress. I’ll make some modifications to improve it in my next post. I want to change it so that the clamp is together in one piece before it’s installed on the cells. At the moment it’s just a bag of bits which won’t stay together until it’s clamped. This is a bit of a design flaw. I can see ways round the problem though.
Just to be clear, I don’t claim to be an expert in anything. This is just a bit of fun.
Note: I’m using 1/4 inch aluminium in this design and the gap between each cell tab is actually larger than that and so when it was all tightened together it wouldn’t look quite as neat as it does in the above images. I think if I was making this I’d probably pack the empty gaps with something to make sure nothing wonders around as the car is moving.