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Jeff Liebermann Jeff Liebermann is offline
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Default Rechargeable battery question

On Sun, 15 Apr 2018 20:31:34 -0700, Mike S wrote:

If you use magnets you might consider grabbing the magnets out of a dead
hard drive, neodymium is IIRC the strongest fixed magnet made, and it
has very low resistance.
https://e-magnetsuk.com/neodymium_ma...teristics.aspx


Those magnets are much too big I have a fairly large pile of such
hard disk magnets that I bought at a local flea market. Very handy,
but not for making button tabs.

The magnets I bought were some of these:
https://www.ebay.com/itm/282388785539
in 6mm x 1mm and 6mm x 2mm. 1mm is a bit thin but works for most
battery holders. 2mm is a bit too thick but works ok in a few
holders. The magnets stick fairly well to the stainless battery case.
I had to punch out a few sticky back vinyl "washers" to keep the
magnets centered.

What do you like for a small spot welder? I've been thinking of getting
one.


I looked at what was available and decided that I didn't like anything
that was also affordable. So, I'm building my own. Nothing fancy.
The biggest automotive starting battery I can find (I want cold
cranking amps), a large high current relay, a less than 1 second timer
board to drive the relay, a foot switch to start the timer, some heavy
gauge wire, and some machined parts for the copper electrodes. It
didn't take much testing to determine that if I wanted to weld
something, I want DC, and to use AC if I wanted to blow a hole in
something. There are several YouTube videos describing how to throw
something together. For example:
"Simple and dirt cheap Spot Welder for lithium cells"
https://www.youtube.com/watch?v=UU7QC5Uby6M
It needs 2 electrodes, no ground clamp, and heavier gauge wire.

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Jeff Liebermann
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Skype: JeffLiebermann AE6KS 831-336-2558