Simple method of punching holes in A123 20Ah tabs

[rwaudio]

I've tried a bunch of different methods of punching clean properly located holes in A123 tabs and nothing was working as smooth and efficient as I would have liked. Drilling makes very poor quality holes, hand held metal punches make better but still poor quality holes and are very tough to get in the right spot. The best thing I had found was a very cheap 3 hole paper punch that I had laying around (doing one hole at a time). This led me to wonder if a higher quality paper punch would do better???

After a brief search I found a Swingline adjustable 3 hole punch, it's "heavy duty" but more importantly it allows you to move the punches around!! The punches are normally aligned with some precut holes in the lower section, but my desired spacing 1" center to center wasn't there. It only took a couple of minutes to drill a new hole and give me the desired 1" hole spacing. This version has some wimpy plastic "margin" adjustments and for those of you who are working with normal tabbed cells they might be handy, my cells are the tabless ones though and I need a very shallow margin, actually a negative margin to put the hole in the desired spot on the tab. I did this with a piece of 0.1875 x 0.5" aluminium bar that I normally use as part of my tab clamp assembly. I cut down the 0.5" dimension to give me the desired depth, but the 0.1875 happens to be exactly the clearance in the frame and the punches (I'm guessing this limits the thickness of paper to be punched). When you tighten the punches down from the bottom it also holds the 0.1875" bar in place as the tab stop.

I set the adjustable end stop to the desired place and taped it on the underside so it doesn't move around. Attached pictures may better describe what I made. Be careful to keep the area of the other tab clear, and please don't try to use 4 punches and do both tabs at the same time!!! This thing is metal and would do a great job shorting out the cell and making quite the show.

View attachment 5

The model # is Swingline #74350, there are others that are very similar, but this was available online in Canada with free shipping. There are replacement punches available so if you wear them out you can simply replace them.











I did around 100 cells in no time at all, it's very quick, easy and repeatable.

 

[Harold in CR]

Excellent. Exactly what I was going to try, IF I ever get the damn cells.

 

[Timmey]

We did something similar to this;

resulting in a 17s1p pack at just 8.5 kg. We'll be using 6 of these packs in series to run a YASA750/Sevcon combo

 

[bigmoose]

Timmey, very nice design! Could you share the detail of the nutplate for your tab clamp? Is it under the pcb?

 

[Timmey]

There is no nutplate under the PCB, it has press nuts in the PCB to attach the tab clamp,

http://www.wavefast.com/web/8888/ns...serReference=97A063B5C8FE86114F82D279&PAGE=48

 

[bigmoose]

Timmey that tip deserves a big "Thanks!" I never thought of using cinch nuts underneath. Simply GREAT idea! Thank you for sharing it.

 

[kfong]

Nice pack design

 

[peterperkins]

Timmey

Can we have a schematic layout for the pcb, design files?

Where did the plastic cases come from?

What are the components along the edges? I note it appears to have some temp sensors underneath.

Thanks

 

[Timmey]

I cannot share any schematics and PCB layouts, since they are not mine to share.

The 'plastic' cases are custom fibreglass boxes we made ourself.

The black connectors along the edges are connectors (voltage and temperature) for the BMS stacked on top of the pack.
So no touchable HV components except from the + and -.

It's all part of this race-car.