3.7v Li-ion battery tabs - can thin Aluminum or copper be used with spot welding?

Thread Starter

RogueRose

Joined Oct 10, 2014
375
So I do not have access to the nickel plated steel that is used to put tabs on rechargeable lithium batteries. I have thin copper & aluminium flashing (for roofs) and both are pretty high purity (about 97% or better) and about as thick as the tabs on the Samsung or Sanyo batteries from laptop power tool batteries.

I've built a large capacitor bank with 35v caps and can select any voltage and then I have a wide selection of caps in parallel (to select the total capacitance of the "tool").

I'm using 2 pieces of 12g solid copper wire or it might be 10g, I forget. They are bonded together to make a nice "press point" where two points will be welded together, but i'm most concerned as to whether the aluminium or copper will work. I would prefer to try aluminium as it is easier to work with, doesn't corrode and is less expensive. Thoughts on this?

Also, I need to figure out a very fast switch that can be sused to discharge the caps (either part of them or entire amoount, As I said it is 35v ('I'm using a 31.8vdc max power supply) can anyone suggest a good switch for this?
 

RichardO

Joined May 4, 2013
2,271
Forget the aluminum. You can't solder to it.

The copper should work if it is not corroded. Copper has a high thermal conductivity so it might be tricky to get the weld.
 

Thread Starter

RogueRose

Joined Oct 10, 2014
375
Can copper be welded to nickle plate? Usually spot welding is only done with similar metals, can't recall ever seeing copper spot welded.
Yeah spot welding will work with dis similar metals, which is why it is great for some things. A quick intense heat mixing the metals then solidifying just as quickly.
 

Janis59

Joined Aug 21, 2017
1,383
Never had understood (except the factory obstacles due extreme cheapness) the ill will to not use the solder. Nickel is wonderfully solderable by means of:
aspirin tablet
concentrated enough ZnCl2 sol in H2O (under 50% not works with Ni)
ortophosphoric acid conc
industrial flush LTI-120
industrial flush "for tinning aluminium"
and many more. Just switch on the soldering hammer and make it clean of colophonia (this is the substance Ni protests)
 

shortbus

Joined Sep 30, 2009
9,322
Yeah spot welding will work with dis similar metals, which is why it is great for some things. A quick intense heat mixing the metals then solidifying just as quickly.
Well if you can do it, aluminum or copper to steel, you had better patent your process. They do steel to aluminum, but both metals get zinc plating first, not bare metals. Steel to stainless steel no problem, they are similar metals, both ferrous based. I think your thunking about percussion welding dissimilar metals, not spot welding.
 

shortbus

Joined Sep 30, 2009
9,322
One of my many industry jobs over the years was spot weld fixturing. The only way I saw copper spot welded was by a laser. The fixture needed to hold both parts very close and with little to no vibration, and had a high failure rate in the end. They redesigned the part and made a crimp instead of weld connection after all of the failed in the field parts started showing up.
 

RichardO

Joined May 4, 2013
2,271
One of my many industry jobs over the years was spot weld fixturing. The only way I saw copper spot welded was by a laser. The fixture needed to hold both parts very close and with little to no vibration, and had a high failure rate in the end. They redesigned the part and made a crimp instead of weld connection after all of the failed in the field parts started showing up.
Do you know why copper welded so poorly. I am guessing that it was a combination of both high thermal and electrical conductivity.
 

Thread Starter

RogueRose

Joined Oct 10, 2014
375
Well if you can do it, aluminum or copper to steel, you had better patent your process. They do steel to aluminum, but both metals get zinc plating first, not bare metals. Steel to stainless steel no problem, they are similar metals, both ferrous based. I think your thunking about percussion welding dissimilar metals, not spot welding.
Ok, that may be correct , the dis-similar metals but I swear I have seen some welded together so I'll have to play around.. I'll have to do some testing once my setup is complete. I have made a bunch of paralleled 35v caps. each equalling about 46200 uf per group, and I have 8 of these.
So each group has the following energy at the given voltage:
35v= 29j/group - 232J total w/ all 8 groups
32v= 23.65/group - 189.2J total w/ all 8 groups
28v=18.25j/group - 146J total w/ all 8 groups
24v= 13.35/group - 106.8J total w/ all 8 groups
20v= 9.25/group - 74J total w/ all 8 groups
16v= 5.9/group - 47.2J total w/ all 8 groups
13.8 =4.4/group - 35.2J total w/ all 8 groups
12v =3.3/group - 26.4J total w/ all 8 groups


Now I have lots of power supplies that are of the above listed values, most are 4-6amps but the 12, 13.8 and 24v are 25+ Amps. I am trying to figure out what is the best voltage to do this welding so I can buy more caps if needed (I use 1000, 2200 and 4400 uf caps - all 35v). I have lots of 12,000 uf 12v caps that I could use if I wanted to go with a lower voltage. I am going to order some more caps when I figure what is the best voltage to go with.

I'm wondering if the different voltage may work for dissimilar metals such as a higher voltage may allow the dis-simlar metals join. IDK, I think it may be worth trying since I have the supplies for the different voltages.
 

Thread Starter

RogueRose

Joined Oct 10, 2014
375
Never had understood (except the factory obstacles due extreme cheapness) the ill will to not use the solder. Nickel is wonderfully solderable by means of:
aspirin tablet
concentrated enough ZnCl2 sol in H2O (under 50% not works with Ni)
ortophosphoric acid conc
industrial flush LTI-120
industrial flush "for tinning aluminium"
and many more. Just switch on the soldering hammer and make it clean of colophonia (this is the substance Ni protests)
I'm trying to figure out what you are saying about ZnCl2 and aspirin. I have LOTS of zinc metal and can make zinc chloride if it is needed. I also have lots of other salts of copper which can be used and some nickel salts which may work for plating some metals.

What is the deal with aspirin?
 

shortbus

Joined Sep 30, 2009
9,322
Do you know why copper welded so poorly. I am guessing that it was a combination of both high thermal and electrical conductivity.
No I never figured why that was so hard. It was for the early oxygen sensor leads on GM cars. In the end they used crimped stainless terminals and stainless wire, the crimp was then laser spot welded to make sure it wouldn't come loose. I do know the copper type cost GM some money due to failure in the field.
 

MisterBill2

Joined Jan 23, 2018
11,579
Never had understood (except the factory obstacles due extreme cheapness) the ill will to not use the solder. Nickel is wonderfully solderable by means of:
aspirin tablet
concentrated enough ZnCl2 sol in H2O (under 50% not works with Ni)
ortophosphoric acid conc
industrial flush LTI-120
industrial flush "for tinning aluminium"
and many more. Just switch on the soldering hammer and make it clean of colophonia (this is the substance Ni protests)
The damage from soldering to the battery cells is that the plastic seals melt. Then problems begin.
 
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