18650 electrode levelling and polishing tool...?

[SniperGaulois]

If someone makes a solderless 18650 box, then it would be useful to have a drill based sanding tool that is able to sand old battery end caps, to take old pieces of solder away and to put a mirror finish on the caps. A tool with 0.1mm accuracy that does surfaces at perfect 90 degrees angles.

It would be cool to have the same tool for the + and - terminals, but the cathode has plastic wrapping on the edge which you'd have to sand away in order to have the same as the anode. Personally that's fine with me, but is it bad practice?

I was thinking of an abrasive drill bit and a battery holder tool where the battery axis is aligned with the drill bit. But that would wear out fast, if the batteries were always in a fixed position relative the the drill disk, it would wear grooves into the disk.

So instead, an abrasive disk mounted to a drill can have to be larger like 10cm diameter and and very precise and probably made of aluminium oxide and the batteries would be in some kind of mounting caddy which is very fast to put at right angles to the drill bit.

I'm well confused about the idea.

 

[liveforphysics]

It's a thin nickel plating on stainless, and the cans on modern 18650's are so thin you really have no margin at all to thin them, which would also remove the nickel and negatively impact contact resistance.

Likewise, no matter how well matched you get them it doesn't matter, as the heating thermal expansion would be a positive temp coefficient to keep the connected ones heating further flowing current and the disconnected ones cooler and contracted from contacting (until it cools down and parallels charged cells with un-charged cells and starts a fire).

 

[SniperGaulois]

There were big flecks of nickel sticking out of some factory defect 18650s and i had to use a superfine aluminium oxide tool, a pierre a faux / scythe stone was the best tool i had for it.

Someone told me they were aluminium, and i was a bit surprised about that because the anodes seem probably like nickel plated steel, the anode is machined differently, a soft metal, it looks like an aluminium finish rather than steel, in some pics here you can see the marks left by one use in an electronic cigarette.

Ecigs are a good test area for high currents using only contact, some ecigs go for about 30w per cell with high output cells, except that's for peak use, I think with abuse a safe solderless box could be rated at about 10w continuous and 15 watt peak. I tested 25w continuous using worst case recycled batteries. Copper can wear out nickel plating fast, aluminium is probably best for any 18650s that aren't welded.

 

[SniperGaulois]

I had a think about this topic, and for reference, here is the best solution i can think of:

The drill handle fixture just above the drill bit gives you a fixed mounting for the drill. Use that mounting to firmly attach an 90' piece of wood with a transverse slot parrellel to the drill disk, like a track so you can drag a little chariot parrallel to the drill disk... make a little grooved battery holder which holds the battery right angle to the drill disk, so the battery can move along the groove parralel while keeping the battery right angles to the disk... All you need is a sanding disk... if they make 800 and 1200 grade sandpaper and drill disks... actually 1600 even. maybe you can 3d print one to hold sandpaper.