@DavidEF, gold would actually be an improvement in contact resistance because of its atomic structure.
That’s a thing I discovered at my new electroplating job: the reason gold is used in contacts is that its contact resistance is extremely low due to its atomic structure allowing a form of cold weld happening, reducing contact resistance by a huge margin.
It’s about as good as a soldered connection, or slightly better at times due to much thinner layer of contact.
This prevents the formation of hotspots, which is very important in small contacts like we have, as this would increase resistance, and therefore heat.
TLDR: In terms of lowest contact resistance:
Absolute best: Gold.
Excellent: Silver
Good: Silver tarnish.
Good: Nickel
Good: Pure copper
Absolute crap: Oxidized copper.
It seems that the biggest difference in our calculations is that you compare pretty much 3.0 to 1.0 while I compare 3.0 and 1.0-like-but-with-3.0-total-thickness.
I think both approaches are right, they just compare different things.
With 25 µm plating thickness like you assume the difference would go up to 13%.
Hmm? Why 13%?
The spring is made of BeCu C17530, and the 50um total thickness layer is made of copper, which is 2,6x as more conductivity as BeCu C17530(100% IACS vs 38% IACS).
If I use your values, I get a 13% improvement, but if I use mine, I get an improvement of 25% at best.
Ah! Ok! I get it now. Sorry. I was comparing the improvement to the 1st gen spring, since it only
But alas, I couldn’t increase the wire thickness to 1,15mm, as not only is it not standard, but it would also compromise spring ability, and by being not standard, it would cost even more than the dual thick copper+silver plated spring.
Did you see my test in that thread? I have an email out to Hank to see what tint bin he used for the D18. It seems to be something different than what he advertises in his store as FB4.
Either that or i’m doing something wrong with my tests.
You have a strong material on the inside and weak on the outside. Mechanically the opposite would be much better.
If you started with a thin solid copper wire and then plated it with LOTS of beryllium copper, the spring would be much stronger.
Or, better, start with a slightly thicker (but still thin) solid copper wire and plate it with a little less beryllium copper. You would retain mechanical properties while improving mechanical properties slightly.
I know.
This would be crazy expensive.
But….
What if you started with thick C17500 spring and reinforced it with 20+ µm C17530? Would that be even possible? Would 20 µm be enough to make the difference?
Have you considered reducing contact resistance with the help of contact plates? Would that make sense?
Well, maybe. The reversing of the tail-cap might cause a reverse gouge. But then, when you’re loosening the tail-cap, you are also relieving the pressure of the spring against the end of the cell. So, it might not be as bad as when you’re compressing the spring.
All that aside, BlueSwordM will be making the new generation springs without a loose end to damage cells. The end will be bent inward.