spot welding battery tabs


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Old 05-11-10, 07:03 PM
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spot welding battery tabs

I was researching the soldering of batteries together to rebuild a battery pack. I saw one where the guy said he took his soldering gun and replaced the "iron" part of the gun with 2 sharpened pieces of copper. He then claimed he could spot weld the tabs on the battery by pressing the tab down and holding the trigger on the solder gun for a second or two.
I do not wish to blow up or short out my solder gun without at least a couple more people saying it will work. My gun is a 75 watt soldering gun. Not sure what size he had. It would be possible to remove the tip and insert the copper wires easily enough.
I have had no sucess soldering the tabs no matter how much I clean them. As far as tinning the tabs first....I can heat those cherry red but can't get the solder to stay on after cooling. I think they are made of nickle but I am not really sure what kind of metal they are. I tried soldering copper wire in place of the tabs but no luck there either.
Anyhow do you think the soldering gun spot welder will work?
 
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Old 05-11-10, 09:50 PM
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I have built up packs by scuff sanding the battery terminal as well as the strap. Soldered up with no problem. You cannot apply too much heat or you can fry the battery. All the guy with the two probes is doing is completing the circuit through the strap. That is not spot welding.
 
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Old 05-12-10, 03:25 PM
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So is my gun too small to allow me to solder or what? Did you use the tabs that came with the battery? I see where I could buy seperate batteries with tabs on them that are pre-tinned, but I thought I had found a cheaper way!~!!
What I actually did was buy a 14.4 battery pack ($20) and remove those batteries from that pack to rebuild the one I can't find unless I want to pay $50 each for them. Of course the configuration was different so I had to disconnect some of the tabs so I cuold build the correct configuration. They were spot welded from the factory. It was easy enough to pry them off but as I see not too easy to solder them back.
 
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Old 05-13-10, 08:25 AM
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Soldering and welding are two totally different processes. Welding does not happen with a soldering iron no matter what size.

Soldering you use an iron to heat the two parts you want to join and then use a third material (solder) to form the joint. Spot welding like used in some battery packs runs a big jolt of electricity through the two parts you want to join. There is so much current going through that the metals heat up to a temp where the two metals fuse together.

Since you have not said what kind of batteries you are trying to solder it's pretty hard to say what you need to do. It sounds like your batteries have chrome or zinc plated steel tabs that need to be welded together but you can cheat and try sanding them, apply flux, and then solder. It can usually work but it is not a truly strong joint.
 
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Old 05-13-10, 10:43 AM
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AH but I did say what kind of batteries I am working on....battery pack for cordless tool.....NiCad. I also stated the tabs are believed to be nickle.
 
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Old 05-13-10, 11:07 AM
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Ah, most of my cordless tools are Nimh and Li-ion though I do have some old DeWalts kicking around that have NiCads. The Li-ions in my tools are in traditional steel cases which are a PITA to solder while my helicopters fly on Li-po batteries that have tinned copper terminals and are easily soldered.
 
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Old 05-13-10, 11:21 AM
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It probably does not help since you already have your cells, but the last NiCad battery pack I rebuilt used C sized cells. I ordered new cells online and I had the choice of getting tabs or no tabs. The tabs were easier to solder than the plain cells I've worked with.
 
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Old 05-13-10, 04:48 PM
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Well I may have to drop this idea and start over.
The new cells with the tabs on them, do you solder the tabs together or do the tabs go to the battery itself? If they go to the battery then I probably will still have issue with soldering them but maybe not. If you do not mine telling what would 12 of those cells cost?
 
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Old 05-14-10, 05:26 AM
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First, if you've already got cells you pulled from the other pack I'd say work with them. They are already paid for so you've got nothing to loose. If they are the steel cased (AA, C...) style. Sand the ends with some fine sandpaper. Apply some acid based soldering flux (most plumbing type solders are this type) and try soldering your wires to them.

If you order batteries you can get them with or without tabs. The tabs come welded onto the ends of the battery. To make a battery pack with the batteries as close together as possible you just connect the tabs together to form the pack. If you need more space between the batteries or your pack is an odd shape then you can solder wires to the tabs to connect the batteries together..

As for cost you need to know what size cell you need and the case style. The cheapest are normal looking AA button tops which you can get for about $.75 each. Normal alkaline batteries like you find at WalMart come in AAA, AA, C, D sizes and have a button top (the positive end of the battery with the bump). You have to be careful because NiCads cells are available in many different sizes and cases styles: 2/3AA, 4/5AA, AA button top, AA flat top...
 
 

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