Spot welding a AAA battery pack

Thread Starter

cmartinez

Joined Jan 17, 2007
7,174
A couple of years ago, I bought a mid-level tack argon spot welder like this one:

1603925944370.png
The machine's working fine ever since, and in fact it's even helped me perform odd jobs such as welding one of the legs of my prescription glasses when it broke due to fatigue, and which is made of titanium.

Anyway, I now need to prepare "battery packs" assembled using four AAA batteries. I've done a little googling around, and I now know that my machine if more than capable of doing said job. And in fact it might even be overqualified. My machine uses a tungsten electrode, whilst the machines that I've seen out there specialized for this sort of thing use a pair of copper electrodes.

Since this is the first time I'm going to experiment with this sort of thing. Here are a few questions that I'm going to try and answer myself before venturing into putting together the first pack:
  • What alloy and at what thickness is best for welding the batteries together​
  • What would the best setting for my machine be for this job.​
  • What type of batteries can be welded using this technique.​
The reason for that last question is that I've already tried welding alkaline batteries, and one of them leaked some kind of liquid immediately after welding the strip of metal to it! ... The strip in question was a small piece of 0.010" stainless steel, and I had to apply two spots for it to properly adhere itself to one of the batterie's poles.

Would this kind of thing also happen if I tried to weld lithium batteries with the wrong settings? And most importantly, is there danger of the batteries bursting (or worse) during the process?

Does anyone here have experience with this sort of thing?
 

jpanhalt

Joined Jan 18, 2008
10,515
One of my first projects was a battery tab welder for my model airplanes. I have used it for 15 years or so. I use copper electrodes, but have thought of changing to tungsten (inserted into the ends of the copper) to get smaller diameter, closer spacing, and still be able to apply enough pressure. You do not want arcing at the contact points. With arcing, you can burn a hole in the battery, which is not good.

I use pure nickel strip. Some people use nickel plated steel. I bought mine from Sunstone Engineering years ago. The price may be higher, but this price does not seem unreasonable: https://sunstonewelders.com/battery-welding-spooled-nickel

The size I use most often is 0.25" x 0.005" for subC and similar NiCd and Lithium ion cells. I have some 0.125" x 0.005" that I have used occasionally. I started with some 0.003" material, but just didn't like how it felt and never used any, except for testing. I have not tried welding to LiPo's.

I do not use a flux of any kind, but I keep things clean and may carefully grind the contact area on the battery, if I feel it is necessary. That is a holdover from the days I soldered them and is really not necessary for welding.

Here's an example of some of my first welds to test the strength. It shows the grinding, which I rarely, if ever, do anymore.

1603928306978.png

Hope that helps.

Edit: Just re-read your post. 0.010 SS seems both too thick and the wrong alloy. You need good pressure and no arcing between the strip and battery case.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
7,174
Yup... 0.010" ss is entirely wrong for this application, as I've just found out after a little digging.

The preferred material is pure nickel, about 0.003" strips if I'm not mistaken.

Thanks for your input, John. It's always thoroughly appreciated.
 

jpanhalt

Joined Jan 18, 2008
10,515
I bought both 0.003 and 0.005 initially. The 0.003 x 0.125 just felt too flimsy, so all I have used is the 0.005 in either 0.125 or 0.25 width. Also got some 0.375 width, but that was too wide. With my larger electrodes (1/4" copper rod tapered to a rounded point) , it is easy to get 4 to 6 welds on the 0.25, as shown. I don't see any reason 0.003 wouldn't work though.
 
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