# Soldering tabs to LiIon batteries



## MrNaz (Aug 26, 2009)

If i have some 18650 LiIons and I want to raise the negative contacts, is it a good idea to solder directly to the batteries, or is that much heat directly against it a bad idea?


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## Capo_au (Aug 26, 2009)

Its a BIG no no to solder straight to any batteries.. If the heat doesnt cause it to vent then it will at least reduce capacity as far as i know.

Take a look in the smoke and fire sub forum for more info on do's and do not's.

Alternatives to soldering are using magnets (which you solder to) or buying a 18650 holder. There are few different types for sale now if you take a look around on CPF.


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## LuxLuthor (Aug 26, 2009)

It's not advised by any battery manufacturers--especially with Lithium Cobalt Ion cells (vs. newer 'safe chemistry' Lithium Manganese & Lithium Iron Phosphate types). Some here have done it (look for post by Fallingwater), but despite him doing it, there is no way to verify if the heat may have damaged plastic separator, pressure protection structures, etc.


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## alpg88 (Aug 26, 2009)

i always do it, i just try to be as fast as i can, put flux on the batt, and a piece of wire i use as tab, than touch it with soldering iron for 2-3 sec, 
i do it in my lights, power tools, laptop batterys, never had an issue. after all they weld tabs at the factory, when they make a pack they heat it up more, melting point of steel is a lot more than of solder, and they weld 4 spots on each end of the tab, i'm pretty sure batts heat up more from that than from solder.


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## LuxLuthor (Aug 26, 2009)

alpg88 said:


> i always do it, i just try to be as fast as i can, put flux on the batt, and a piece of wire i use as tab, than touch it with soldering iron for 2-3 sec,
> i do it in my lights, power tools, laptop batterys, never had an issue. after all they weld tabs at the factory, when they make a pack they heat it up more, melting point of steel is a lot more than of solder, and they weld 4 spots on each end of the tab, i'm pretty sure batts heat up more from that than from solder.



 Obviously, you are wrong about what you are speculating...so people should consider the source. 

All manufacturers spot weld tabs and battery packs. None of them solder to cells...not even to NiCad or NiMH. Learn the facts about spot welding before making unsafe and misleading assumptions. 

Again, no one should consider soldering to Lithium Cobalt ion cells.


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## alpg88 (Aug 26, 2009)

i never said mafacturers solder, i said weld, i know what spot welding is, it is hot. those spots are red hot after welding, i,ve seen it with my own eyes, thou it wasn't battery i spot welded, but imo prosses is the same, isn't it??? if not tell me how do you spot weld anything without getting it hot, i know of 1 way, but it isn't aplicable to batts. 
speculation you say, well the fact that i do it, and never had an issue, tells me something, 

hey i'm not saying he should do it, it is his choice, but i do it and never damaged single cell.

manufacturerd don't recomend lots of things, i can't blame them most pp do it wrong, than sue the manufacturer.


to o.p. there is a conductive glue, you could try that.


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## LuxLuthor (Aug 27, 2009)

I have a battery pack spot welder from Sunstone Engineering. I have spot welded at least 1500 cells. I have soldered 250+ NiMH cells. Capacitive spot welding which all battery pack manufactures use because it is safe, and does not in fact heat up the metal, nor damage underlying battery structures as you are imagining. I have immediately put my finger over the spot weld with no palpable heat. I could explain why this is the case, but on this limited topic I am sure of my statements. 

There are many very good reasons why battery manufacturers don't solder to any cells, but especially not to *Lithium Cobalt chemistry* cells. It is downright dangerous.


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## alpg88 (Aug 27, 2009)

well you are right about capacitance welding it is colder than soldering, my experience with spot welding was different (thou it was a lot thicker mettal), turns out i do similar thing evertime i zap nicd, i'll try using the same circit i got to weld tabs, or something similar.
so thank you for that info,


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