Topic: DIY battery tab welder

[fmctm1sw]

I've finally had some time to work on this, it had been in the garage for years now.  I paired a Lambda 20VDC power supply, a big car audio capacitor, and a massive silicon controlled rectifier to weld battery tabs.  The SCR will fire when a momentary switch triggers it. 

After a few small issues (wrong type switch for one), we actually welded some tabs.  It's a little tedious but for a few simple projects I have it should work fine.  I just bought a decent foot switch that will leave both my hands free.  My boy had been working the switch while I used the leads.  I also bought some superflex 6 ga cable to make it easier to manage the leads.

I got the inspiration from a website years back.  You can see the welder blew holes in the nickel strips as we were having issues with the switch..

[xtravbx]

Can you explain what you're using this for? It's function? Explain it like you would to a 10 year old.


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[dusterdude]

What he said

[fmctm1sw]

It allows you to weld batteries together basically with little nickel tabs.  Those battery powered tools have a bunch of rechargable batteries strung together like this:http://www.instructables.com/file/FKC6ZKOH2WEY16A
Soldering them like that creates too much heat for the battery though, hence the idea of spot welding.  Lot of applications like RC car batteries, airsoft batteries, custom batteries, etc, etc...

A few years back I bought a new battery pack for my Roomba (supposedly) rated at 3500ma/h.  After the battery died I took it apart and found the batteries rated at 2100ma/h.    So I decided to try to make my own.  All the battery pack consists of is 12 sub c batteries strung together in series and a little temperature sensing component.

Edit:  like this:  http://www.schneordesign.com/Avi/irobot/roomba_battery_mod_byAvi_3.jpg 

[dusterdude]

Interesting,thanks

[BobbyR]

Good information and a very clever solution.

[fmctm1sw]

Here's my first product, a roomba 500 series battery (OEM on left, mine on right).  It ran my roomba for about an hour.  They were only 1500mA/h batteries though since I didn't want to go all out if it was going to fail.  Next up is taking my cordless drill apart...

Oh and the superflex cables didn't seem to work.  They didn't seem to carry the current for some reason.  Foot switch works great though...