MY HOMEMADE BATTERY SPOT WELDER

**mariost** · Apr 13, 2019, 02:24 AM

A very useful homemade construction. We can safely connect all kinds of rechargeable batteries. We need a car battery between 35-44 Ah (Here the battery is 100 Ah but we don't need so much current) , a strong relay from a scooter or a motorbike or from a car ( the ignition relay) . The electrodes must be from bronze or from copper. We also need a small switch to give in an instant the order to the relay to close the circuit. We must push the electrodes on the battery but not very hard to not destroy it. The batteries don' t become so hot because the time we need to weld is less than 1 sec. This method is much better than to weld with soldering iron, witch makes all the area very hot. Take care of your hands to not burn them. Rings , bracelets and other metal accessories are forbitten to wear during the welding.

**DIYer** · Apr 13, 2019, 05:42 AM

Thanks mariost! We've added your Spot Welder to our Welding category,
as well as to your builder page: mariost's Homemade Tools. Your receipt:

Spot Welder by mariost

tags: spot welder, battery

**olderdan** · Apr 13, 2019, 10:28 AM

Originally Posted by mariost

A very useful homemade construction. We can safely connect all kinds of rechargeable batteries. We need a car battery between 35-44 Ah (Here the battery is 100 Ah but we don't need so much current) , a strong relay from a scooter or a motorbike or from a car ( the ignition relay) . The electrodes must be from bronze or from copper. We also need a small switch to give in an instant the order to the relay to close the circuit. We must push the electrodes on the battery but not very hard to not destroy it. The batteries don' t become so hot because the time we need to weld is less than 1 sec. This method is much better than to weld with soldering iron, witch makes all the area very hot. Take care of your hands to not burn them. Rings , bracelets and other metal accessories are forbitten to wear during the welding.

Very resourceful,
It reminds me of a time when my father and I got my old Ford Anglia through its MOT by using two car batteries to weld the bodywork for suspension hangers. We used this device which was on sale many years ago.

MY HOMEMADE BATTERY SPOT WELDER-untitled.jpg

It has a coil which helped the electrode maintain an arc.
I would only recommend using lead acid type batteries for this.

**Priemsy** · Apr 15, 2019, 07:39 PM

Would like to see a build diagram of how everything fits together mariost. It looks a neat project to do.

**Priemsy** · Apr 15, 2019, 07:43 PM

The Anglia was my first car after I got my license. Oh, the memories of those days gone by.

**VinnieL** · Apr 15, 2019, 08:09 PM

I understand the operation and building all except the actial head that holds the two electrodes. How and what is the holder made from and ? Great Idea!

**Rorschach** · Apr 16, 2019, 12:14 AM

I would definitely like to see some more detail on this. I have several spare car batteries on hand and a tool like this could be very useful for me.

**mariost** · Apr 16, 2019, 01:12 AM

I ' ve put hot shring tubes (double) around the end of the two cables and I've connected the cables with two wires 2.5 mm from bronge soldering wire. I put the wirew in a ceramic cable connector and to the ather side i put two pieces of th same wire aw like electrodes (to be easy to change them (you can also use nail from bronze or copper (after you cut the head) but I didn' t find it at the local store.It' more correct to use a battery between 35-40 Ah. 200 A of short circuit current is enough and the use is more soft (here is a little violent). The battery must be in a good condition (not very old). it' s better also to put a 10 W fuse in serie to the coil (only here not at the high current).