Copper strips versus nickel strips on battery packs?

[alfantastic]

Reference: Samsung 30Q 12Ah pack. Maximum current draw 25 amps.

Would this pack built using copper strips, have any significant advantages over the same pack built using nickel strips?

I've been told by the builder that the copper strips will give the batteries a much longer life. Is this bullshit?

 

[spinningmagnets]

Copper is a huge hassle to use right now, but many people are working on it. Copper is cheap and available, and it should remain cheap for the foreseeable future. Where it is most useful is in a small battery pack that has cells that are capable of putting out very high amps, because nickel has much more resistance.

Nickel is affordable "right now". It is acceptable for a pack with a low total amp output. However, even if you add a thicker nickel strip, or multiple layers of nickel...it has high resistance. Some of your watts are being converted into heat, with the bus strips being the heating element. It is this resistance that makes nickel easy to spot-weld on an assembly line. It can be done quickly with a high level of reliability.

Copper is difficult to spot-weld, but there is a thread discussing the use of copper strips that are held onto the cells by magnets. Nickel is very corrosion-resistant, and copper busses would need some type of coating to inhibit corrosion and oxidation.

I don't think either one would be better or worse for longevity.

 

[alfantastic]

Big thank you spinningmagnets for the informative reply. When you say nickel is acceptable for a pack with a low total amp output, would you consider a maximum draw of 25 amps on a Samsung 30Q 13s4p pack, to be in the low category?

 

[spinningmagnets]

12-Ah from 3000-mAh cells is 4P

25A from 4P is less than 7A per cell. A 30Q pack like this will almost never get warm, if 25A is the occasional peak draw of the system. This good, it means the pack should last a very long time since heat erodes its life-cycle count. you will be fine at 25A.

 

[amberwolf]

some other discussions
https://endless-sphere.com/forums/search.php?keywords=copper+nickel+strip*&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search

 

[want to build]

Copper is a huge hassle to use right now, but many people are working on it. Copper is cheap and available, and it should remain cheap for the foreseeable future. Where it is most useful is in a small battery pack that has cells that are capable of putting out very high amps, because nickel has much more resistance.

Nickel is affordable "right now". It is acceptable for a pack with a low total amp output. However, even if you add a thicker nickel strip, or multiple layers of nickel...it has high resistance. Some of your watts are being converted into heat, with the bus strips being the heating element. It is this resistance that makes nickel easy to spot-weld on an assembly line. It can be done quickly with a high level of reliability.

Copper is difficult to spot-weld, but there is a thread discussing the use of copper strips that are held onto the cells by magnets. Nickel is very corrosion-resistant, and copper busses would need some type of coating to inhibit corrosion and oxidation.

I don't think either one would be better or worse for longevity.

hi
-im trying to understand your use of the word bus strips . could you point out a picture that show what is it and its use plz

- Also what woud be the consequences of corrosion and oxidation in a battery that would use copper without coating?

tx

 

[spinningmagnets]

Here are bus "strips". Copper is good for series high amps...nickel is perfect for parallel connections. Having the nickel on top of the copper as they cross over the cell-tip allows the copper to be spot-welded.

Here are bus "plates", where one layer performs both the parallel and series connections.

parallel below, 4P

series below, 7S for 24V

 

[veer]

Here are bus "plates", where one layer performs both the parallel and series connections.

Hello
How were these connections made though? Copper is still hard to spot weld and protect against corroding. What is this welding technique?

Also, if I am able to find someone with laser welding machine, can that be used to weld copper to lithium batteries? Anyone known to do so, copper bus bars connected by laser welding!

 

[spinningmagnets]

This is the "copper/nickel sandwich" method.

Copper and aluminum take extremely high amps to spot-weld by themselves. However, if you put nickel over the copper, the resistance of the nickel turns the current into lots of heat.

This means you get an adequate amount of heat in a tiny spot, with much less watts/joules of energy.

The best cap for this method is nickel-plated steel, but pure nickel works in the power range of the small kWeld and Malectrics welders.

 

[pullin-gs]

What is order-of-welds?
Do you weld copper strips onto battery terminals first? Then weld nickle strips?
Or do you lay UNWELDED copper strips down and lay nickle down on top of the copper......then weld....heat generated is enough to weld nickle to copper AND weld copper to battery all in one operation?

 

[Bobby June]

What is order-of-welds?
Do you weld copper strips onto battery terminals first? Then weld nickle strips?
Or do you lay UNWELDED copper strips down and lay nickle down on top of the copper......then weld....heat generated is enough to weld nickle to copper AND weld copper to battery all in one operation?

You might already know, but to add some words, the copper and nickel are both placed onto the battery and welded at the same time. The heat is diffused and, like SpinningMagnets said, the heat is used as a device that is there to help the spot welded copper bond to the battery. That added heat keeps the nearly resistant-free copper atoms liquified (to a degree) longer than without the heat. Resistance seems to be loved for something like this, when usually it not. And no worries about this nickel add-on. Current flows in the copper and doesn't even know nickel is around.

To add to this is the application of flux onto the battery before you lay down the copper and nickel. This, I believe and have done myself, increases the strength of the application and might increase the current flow. Someday I'll give it a test to see if both of those results are true and reply again.