Why Is Lead Solder Welding Not Popular?

[SniperGaulois]

There are solder alloys that melt at 130-150 degrees, and my Panasonic batteries can handle 220'C according the the specifications. With 90 degrees to spare prior to overheating the batteries, it should be possible to weld them. Most of the research has gone towards spot welding, when it could be possible to weld the batteries normally. So with 140 degrees solder, if you put all the batteries in a line, perhaps it's possible to weld one battery every 10 seconds... Afterwards, it would be only necessary to line up some nickel strips or 14awg aluminium? it's more conductive than nickel, and to make batteries in a way that is more reversible that spot welding. why dont people use aluminium, it is so cheap and it is more than twice as conductive as nickel? aluminium is used in power grids and airplanes: https://en.wikipedia.org/wiki/Aluminum_wire it's light and it can be used for low temperature welding. I could well see myself getting some 140 degrees top range solder, aluminium ribbon, and making a pack in that fashion, now that i have just bought 150 euros of spot welding equipment online. a waste of money?

 

[friendly1uk]

Well I haven't unboxed my welder yet, so I'm very interested. I never thought to check the temps a battery can handle. I can't believe I have been such a sheep. Typical 60/40 multicore melts around 180 so if my cells can reach 220 I have been very much misled. I do hope not.

 

[redilast]

They can handle 220C? Source?

The ones I have specifically say not to heat above 212° F, which is 100C, way below 220C.

Also cells with PTC devices equipped can be damaged and have irrecoverable resistance increases because of heating them up too much causing the PTC to change phases but never completely reach its factory low resistance state.

 

[Hillhater]

I Suggest you try soldering some aluminium strip, before you get too excited ! :wink:
If you want to solder, use copper strip.
And yes the more lead in the solder, the easier it it is to use.

 

[Voltron]

All of the low temperature ones have low joint strength and high corrosion according to the chart. And I sure wouldn't want the solder to start melting during some high amp load heating... it seems like runny solder and metal strips floating loose in the battery would be a recipe for disaster.

 

[Hillhater]

If you have cells/conductors/joints hot enough to melt any solder, you already have big problems before anything starts to come loose !

 

[SniperGaulois]

Thanks for the info's. I was wrong to say that the panasonic automotive cells can handle 220'C, all lithium cells perform a runaway heat production reaction beyond 120-130. I couldn't find any solder at 118 degrees, i did find 500g / pound tubs of SD528 low temp solder on aliexpress for 30 dollars so i have a lot of that, will be convenient for working with lithium cells.

 

[Chalo]

I have used pure indium as solder for LEDs and controller leads. It flows at about 300F and has better thermal and electrical conductivity than normal lead solder. It's expensive, though.

I would expect a battery to be at least slightly damaged by heating if I got a good solid fully wetted joint using indium.

 

[Ohbse]

Why Is Lead Solder Welding Not Popular?

Because it's worse and damages batteries. Spot welding is easy, reliable (if cell packaging is done correctly) and cost effective beyond the initial investment in tools (now days not much money)

 

[Syonyk]

Every spec sheet I've read by battery manufacturers says, in some words or another, "Do not solder to batteries, spot weld only."

I can put my finger on a completed three-zap spot weld and it's warm but doesn't burn me right after I'm done.

Even "low temperature" solder will do serious skin damage if you touch it immediately after making the joint.

 

[SniperGaulois]

Every spec sheet I've read by battery manufacturers says, in some words or another, "Do not solder to batteries, spot weld only."

Tesla doesnt spot weld their battery packs, it seems that they are soldered.

So what about this for a plan: Use a low melting point allow that melts at 80-100 degrees, and use it as a combined fuse and contact...

If the battery rises beyong 80 degrees, which is generally to be avoided at all costs right? for longevity etc... The fuse would melt anyway...

The cost of soldering on an 80'C wire onto the battery in the first place, would raise the cap of the battery within it's specified range but much higher than the 40 degrees that a well constructed pack should be at:

very interesting list:
Rose's metal 98 °C (208 °F) no 50% 25% 25% – – – – –
Cerrosafe 74 °C (165 °F) no 42.5% 37.7% 11.3% – 8.5% – – –
Wood's metal 70 °C (158 °F) yes 50% 26.7% 13.3% – 10% – – –
Field's metal 62 °C (144 °F) yes 32.5% – 16.5% 51% – – – –
Cerrolow 136 58 °C (136 °F) yes 49% 18% 12% 21% – – – –
Cerrolow 117 47.2 °C (117 °F) yes 44.7% 22.6% 8.3% 19.1% 5.3% – – –
Bi-Pb-Sn-Cd-In-Tl 41.5 °C (107 °F) yes 40.3% 22.2% 10.7% 17.7% 8.1% 1.1% – –
Galinstan −19 °C (−2 °F) yes <1.5% – 9.5-10.5% 21-22% – – 68-69% <1.5%


some of these are used as solders. if you use cerrosafe for example to construct a battery that is specified to always be under 45 degrees, i.e. completely cool, it would be awesome wouldn't it?

 

[Chalo]

Most of the exotic low melting point alloys have poor electrical conductivity. That's why I've used pure indium when I need a low temperature solder, even though it has a higher melting point and is more expensive than Woods metal etc.

 

[spinningmagnets]

I believe Tesla uses ultrasonic vibration friction welding. The pulse is measured in milliseconds, and the frequency is unusually high. I'm not sure of the proper term...Seems to be working well for them, so it's hard to find something to criticise about it...

[edit] Found it:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=79950

 

[PaulD]

Has anyone considered resistance soldering using pre-tinned busbar or maybe thin ribbon solder between the cell and busbar? Maybe this would allow us to use the $100 alibaba spot welders with 0.2mm brass or copper... This should reduce heat duration significantly compared to a solding iron.... I think I'll try it, but there's probably a reason nobody is doing it.

 

[spinningmagnets]

Paul....DO IT!

"If I had asked what customers wanted, they would have said, make a faster horse" -Henry Ford

 

[Syonyk]

Tesla doesnt spot weld their battery packs, it seems that they are soldered.

No, they're high frequency ultrasonic welded.

https://chargedevs.com/features/a-closer-look-at-wire-bonding/

Has anyone considered resistance soldering using pre-tinned busbar or maybe thin ribbon solder between the cell and busbar? Maybe this would allow us to use the $100 alibaba spot welders with 0.2mm brass or copper... This should reduce heat duration significantly compared to a solding iron.... I think I'll try it, but there's probably a reason nobody is doing it.

I doubt they'll get it hot enough to melt solder.

 

[SniperGaulois]

I just received a SnBi solder in the post, 30 dollars half a kilo of it arrived within a week, will be good for all the 12g wires hopefully.
comparison with standard solder:

 

[markz]

Maybe this would allow us to use the $100 alibaba spot welders

Why bother with Chinese junk?
I like my MOT welder with timer from a man in Europe.
http://www.avdweb.nl/tech-tips/spot-welder.html

 

[Overclocker]

I have used pure indium as solder for LEDs and controller leads. It flows at about 300F and has better thermal and electrical conductivity than normal lead solder. It's expensive, though.

I would expect a battery to be at least slightly damaged by heating if I got a good solid fully wetted joint using indium.

nice. i've always wanted to solder the dice of computer CPUs directly to copper waterblock w/ indium solder. never got to do it though...

 

[SniperGaulois]

Here is a home portable ultrasonic welder: OH DREAM
except that the video is hiding a box as big as a spot welder away from the camera.

https://www.youtube.com/watch?v=q-CJ69Wz4NQ