[chbot] Battery spot welder

Helmut Walle helmut.walle at gmail.com
Wed Jun 2 09:28:48 BST 2021

Hi Wallace,

from memory... there is no shortage of battery spot welding tutorials on 
Youtube. The quick and dirty DIY method essentially consists of an old 
car battery (a new one would theoretically do as well, but as your 
project is about recycling, using new equipment might be self-defeating 
in this case) and a few wiring cut-offs (again, thinking up-cycling 
here), something like 2.5 mm^2 single-strand insulated copper wire. The 
conceptually simplest (no built-in safety - so that would be something 
to add for any practical application) method connects a piece of wire to 
each battery pole, and then the ends of both wires are pressed down onto 
the nickel strip that is to be welded onto an end of a cell, with the 
contact points about a couple mm apart. The exact current probably does 
not matter too much, as long as it is high enough to get the required 
amount of energy into the welding spots quickly (slow-cooking would lead 
to excessive heat dissipation, which is neither good nor safe for the 
cell being welded onto). Experiment to get the timing right (and as 
target times ought to be something like a second or even shorter, this 
may require an electronic timer and a beefy contactor for switching the 
welding current), keeping in mind the amount of energy is proportional 
to I * I * t, where I is the welding  current, and t the duration... the 
welds should hold better than the surrounding nickel strip; so if you 
are trying to pull the nickel strip off it should tear. If the nickel 
strip comes off easily without visible damage to the strip, the energy 
was too low, and the weld did not get hot enough.

And make sure you get the appropriate nickel strip for this purpose (I 
believe it's something nickel, but don't take my word for it.).

That's it in a nutshell; HTH & YMMV.

Keep us posted on path chosen and outcomes, please.

Kind regards,


On 2/06/2021 09:02, Marshland Engineering wrote:
> I've got heaps of old batteries. Some may be worth recycling.  There are many
> types and brands of spot welders on Aliexpress. There seem to be 3 options,
> battery, supercap or mains with a microwave transformer. Can anyone recommend
> one, or, a good reliable method including what probes to use.
> Thanks Wallace

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