2170s without a tab

higher_wire

higher_wire

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Aug 30, 2017
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Have any of you worked with cells that don’t have a standard nickel-steel tab? I’m working a development program for an EV startup, and they asked me to spot weld 2170 cells. Problem is, the positive electrode is aluminum and I’m unable to spot weld nickel or solder copper wire. Any ideas?
 

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Highly conductive epoxy and glue a nickel cap to the top?

Definitely an interesting situation, though. Please keep us updated if you find a way that works with good results. Those 2170's will be becoming more and more available in the coming few years.
 
Maybe spot weld with thin aluminium strip vs nickel, then at eventual end of aluminium strip, do a hole, bolt to copper lug, treat for corrosion.
I'm thinking spot welder Amp setting would need to be a far bit higher than for nickel due to lower resistance.
You'd have to sand paper clean both surfaces just before the spot weld to get the oxide layer off.

Maybe a mechanical holder with spring contacts (not stainless steel, aluminium reacts with that...).

Any metal to metal with aluminium is going to have oxidisation problems eventually.

Poor choice of cell really!
 
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If going with springs, or metal press fit contacts, I think beryllium copper alloy would probably be one of the best. And it's not very expensive. You get the conductivity of copper with the none rusting (aka oxidation) of the beryllium.

Reading Repackets post....
Redpacket said:
Maybe a mechanical holder with spring contacts (not stainless steel, aluminium reacts with that...).
Click to expand...
you could have this holder with "screw" contacts instead of springs. A screw that has a wide tip that would press against the cell would be threaded and held into place by the holder. Then each cell is tightened to a specific torque value, say 10in-lbs. (1.14nm) (this value would need to be calculated to get best contact/current capability w/o damaging the cell).
With the right design, it would allow for serviceability of the cells, have good functionality, and it would look nice
 
Redpacket said:
Maybe a mechanical holder with spring contacts (not stainless steel, aluminium reacts with that...).
Click to expand...

They have these for 18650s but I haven't seen them for 21700s yet.

(Hmmm..... Why can't I post that link here? What is it about that web site that is getting censored? Here's the shortened link.)

https://*******.com/product/vruzend_basic_kit/
 
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The product is garbage from what I have read. No first hand knowledge.
Forget what the circumstances were but whatever they were led the adminof this forum to censor the site.

Later floyd
 
floydR said:
The product is garbage from what I have read. No first hand knowledge.
Forget what the circumstances were but whatever they were led the adminof this forum to censor the site.

Later floyd
Click to expand...
Ooops! I didn't mean to circumvent a ban. I'll pull my shortened link and leave the censored one in place.

Apologies.....
 
No worries. yeah, they were banned due to several reasons. That product doesn't come up much, tho. so not much of an issue is made of them :p

Also, I haven't seen the cell holders for 21700's yet, either. There is for the smaller cell that's between the two, tho. But, that won't help much in this situation.
 
I'm also thinkering how to repurpose these 2170, they start to become available from salvage crashed Model 3 in Belgium as well.
Ignoring the fact that it takes a lot of effort to extract these cells they yield a very interesting €/kWh rate.

Spotwelding seems not to be realistic with kWeld like solutions, maybe a static aluminium terminal on the positive side and a springy part on the negative terminal that presses everything together? And then engineer it in a solution to create 60p pack?
 
DiggsUt said:
They have these for 18650s but I haven't seen them for 21700s yet.

(Hmmm..... Why can't I post that link here? What is it about that web site that is getting censored? Here's the shortened link.)

Click to expand...
Because I've personally had bad experience with the product and refuse to give them a second of air time.
 
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