So yeah that is pretty much my question.
What are the best ways to put a button top cap on a 18650 battery?
Is using solder a must?
Can it float and just use a washer and the heatshrink to keep it in place?
What are the dangers?
Thanks
Button tops are typically spot welded on at the factory. It makes a good connection, but they don’t get as hot as soldering.
The other problem is the button cap you used shorting out the battery case. The little white ring under the shrink wrap on the positive is all that’s keeping you from having a big hot mess. Anything loose or floating is liable to saw or rub throught the insulator
I ordered 30Q button tops in the group buy and am fully expecting I’ll receive flat top batteries .
I am going to affix some small disc magnets to them with JB Weld .
You too?
I even bevel the edges of the magnets slightly with a diamond file …
That is exactly why I put this thread up, I ordered 8 that turned out to be flat.
But I don’t wanna mess with magnets or solder blobs so hence the question.
Guess I have to wait for banggood to fix it.
For I cannot spotweld.
You need to build yourself a capacitive discharge welder 
Like this: Zero Emission Vehicles Australia
That spot welder is tempting to build!
Does JB Weld conduct electricity? Or I guess you just put it around the outside of the magnet?
I’ll solder 5x1.5mm magnets…
Good question.
If it was , a magnet could be applied on top of a small blob , and the magnetic force would squeeze most of the weld to the outside of the magnet , where it’s most needed to withstand shear force …
And that would simplify the process greatly .
Just got through Oogling it , Non-conductive .
Conductive adhesives do exist , though .
Like Wire Glue
Is this to give it a button top appearance? If the magnet was filed at 45 degrees on the side pressed against the battery, wouldn’t that give the glue a greater surface area to work with without getting it between the magnet and battery?
My intended use is in a SRK , I don’t want to wear out the contact ring .
Your idea sounds good . I will scuff the cell top .
Careful, the coatings on my little magnets flake off fairly easily. I hope yours are made better than mine.
With all the methods considered please keep one thing in mind: it can add a substantial amount of resistance to the internal value. Not a good idea to do this to such a high drain cell like the 30Q. Stainless steel or nickle plated steel buttons may have way poorer conductance as desired, especially when high currents are drawn. For those who speak German (or can get some translation) I’ve found some measurements of Keeppower cells with and w/o an additional button (even welded to the cell) here:
It makes no sense to bypass every flashlight spring with copper and then add unneccessary resistance to the cells.
Of course, it has to be tested in this particular case. If someone who has got both button and flat top 30Q’s from Banggood could compare the resistance e.g. with an Opus charger or some other way it would help to proof my case (or the opposite).