diy spot welder

black bob · 04-07-2007, 12:52

hi iam an newby.can anyone give me info on making a spot welder for cacmium batteries? i want to make my own packs up for model making ,yhe cost of per packs are rediculous .i have a hp photo printer that takes a battery ,but the cost is almost half the printer and camera together £60.00 ,the set cost £139.00.so you can see that it is cheaper to buy and make up your own set!!hopefuly bob

Richie · 04-07-2007, 17:53

Hiya Black bob, welcome to TheDIYforum

I assume your referring to "Calcium batteries" which ideally shouldnt be spot welded as this is too hot and will damage the batteries.

You will often find that these are simply soldered together, then the strength to hold them together comes from the plastic that you shrink over them which holds them all together.

The solder is mostly just to ensure good electrical contact and isnt actually for any strength, and if you have any old cordless telephones, take out the battery pack and once you remove the plastic wrappings you should see that the connections are simply lightly soldered, especially where the batteries are not all in a straight line, little peices of copper are soldered over the terminals to join them together.

See the image I've attached to show a typical rechargable battery pack for a radio controlled plane.

Hope this helps Bob?

black bob · 04-07-2007, 18:12

Quote:

Originally Posted by Richie

Hiya Black bob, welcome to TheDIYforum

I assume your referring to "Calcium batteries" which ideally shouldnt be spot welded as this is too hot and will damage the batteries.

You will often find that these are simply soldered together, then the strength to hold them together comes from the plastic that you shrink over them which holds them all together.

The solder is mostly just to ensure good electrical contact and isnt actually for any strength, and if you have any old cordless telephones, take out the battery pack and once you remove the plastic wrappings you should see that the connections are simply lightly soldered, especially where the batteries are not all in a straight line, little peices of copper are soldered over the terminals to join them together.

See the image I've attached to show a typical rechargable battery pack for a radio controlled plane.

Hope this helps Bob?

hi thanks for the input,but batteries that are in packs hve tags welded onto them and the welded straps are only attached by a tiny spot weldd ,so the weld only requires a fraction of a second or so there is no overall heating of the cell .i have used the full sized spot welders ,and even they only take seconds to weld depending on the gauge of the metal.i think that a brass or copper bit would be needed and with a very narrow flat point on it.what i need is the size of transformer and size of the points .one idea that i am toying with is a ring that goes round the tip and is placed on the terminal that the tip and comes through and welds the strip

Richie · 04-07-2007, 20:24

Thanks Bob

I think a picture of what your doing here might actually speak a thousand words.... Show us what your doing?

drystonewall · 05-07-2007, 19:05

Hi,

Been thinking about this question and I am not sure it is a good idea to experiment here as I think the tabs are put on before assembly of the battery.

I take into account the other warnings here but........

If you think about it for a moment, trying to put a high enough current through the battery to weld the tag to it is at least going to shag it out and at most make the battery explode in your face.

Please do not try this!

Tandy, god rest their souls used to do a heat free solder paste that was used like an epoxy type resin. that, if you could find a product like it might be your only ticket out of here.

I have had a quick look around for it with no luck,

best wishes and dont blow yourself up,

Nigel.

Richie · 05-07-2007, 21:15

Quote:

Originally Posted by drystonewall

If you think about it for a moment, trying to put a high enough current through the battery to weld the tag to it is at least going to shag it out and at most make the battery explode in your face.

Hey

Excellent point Nigel, highlights my point about soldering instead of welding.

Soldering only relies on heat, of which you can easily keep away from the batteries by actually soldering the small joining tab first and putting it in place before the solder sets, whereas welding is just asking for trouble.

Even without the current, the extreme heat (Albeit for a few seconds) would damage the battery as batteries do have small temperature limits (Check with each battery for these) but also, as Nigel says, welding relies on passing a current through the item to generate its heat, so you WILL end up with a dead battery, but one thats really well held together though