Brass for spot-welding 18650 parallel cell groups?

Maybe this thread would help?
https://endless-sphere.com/forums/viewtopic.php?f=14&t=85140&hilit=copper+tape

There are also other bits of info about it that are hiding in this list:
https://endless-sphere.com/forums/search.php?keywords=%22copper+tape%22&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Guys I worked out how to get copper to weld onto battery's

1. Clean everything with vinegar especially the welding surfaces
2. Flux the area with a flux gel
3. Cut a small piece of solder, I like using silver solder you can use what you want
4. Put that small piece of solder on the welding area
5. Place the copper or metal piece on top of the solder
6. Press the spot welder very lightly onto the metal weld area and Weld

The trick is to make sure not to press down to hard as you will push the solder out, this method is soldering using the spot welder takes practice but works

What volts, amps, and pulse length did you use? Also, what thickness of copper ribbon?

Thanks for posting this...as far as I know, this is a really new thing. Maybe more complex than a large battery assembly line would want to do, but for a low-volume garage builder, it seems like it would definitely be worth the time and effort.

My red brass arrived today thanks spinning magnets!
My first impression is that it is annealed yellow brass, but I'm not sure ( I might try and figure it out)
Anyway I did some initial testing with it. It was .33mm thick so I beat a few bits out to .2mm -it's quite soft.
At 0.2mm it spot welds exactly like the 0.2mm yellow brass which I would say is good but not excellent. It takes more power than equivalent thickness in nickel, is a bit less consistent and is quite a bit weaker. But it's pretty good over all. I'd say that if you want to experiment with something similar, get yellow brass cause it's easy to buy.
So then I tried the full .33 ml. Even with stupid power I couldn't weld it... And it blew holes in the can if I messed up with that much power
But, then I slotted it.
.33mm red/yellow (whatever it is) brass welded really well when slotted. It took a mild increase over .2mm nickel ( un slotted) but was much stronger and more consistent than the .2mm brass
The slotting does suck, cause it's hard to do mid strip, but this might be a good option for high current series connects.

I also did .1mm pure copper for reference. Welds moderately easy, but is inconsistent and fractures around the weld if you slightly overdo it. This leads to significant weakness ( it's already really weak)
All these test were even better if welding to nickel not just the can. Leads me to think that say .1mm nickel in broad sheet laid down first for the parallel group with .3 brass for the series connects might be really good.
Lots more testing to do...
One of the copper alloy suppliers said they'd see what they could do with my request, but I haven't he heard any further yet.

Standard common C230 yellow brass is a mix of copper and zinc. The more copper an alloy has, the more conductive it is, and also the less resistive it is. However, the more resistive it is, the easier it spot-welds, because when you pass current through a tiny spot, that spot will get hot enough to melt the two pieces together.

Pure nickel is OK for mass-produced battery packs. It has high resistance, so it spot-welds VERY easy on a mass-production assembly line. The thing I am addressing is two-fold. Nickel will get expensive in the future, so what are our options? Second...we are not interested in low-performance battery packs. Did anyone buy a spot-welder just to make their own 20A packs?

If you want 40A to 80A peaks from a DIY battery, using nickel means you are spending some of your battery watts heating up the nickel strips like they are nichrome wire in an electric room heater. If you double the nickel strips to cut their heat in half, you are still wasting the same amount of battery watts making your battery warm, it's just that the heat is spread across more strips (for less voltage drop).

Corrosion of copper/brass is easy for a DIY builder to deal with, by using a coating or DIY plating. Plus, making the connection between the parallel strips and the series flat-bars is also easy. It is only the spot-welding between the parallel strips and the actual 18650 cell ends that is troublesome.

Material______Copper____Zinc___Conductivity___Price______ability to spot-weld

Copper_______100%______0%_____100/IACS______Cheap______hard
C40410_______98%_______1%_____68/100________Expensive___easy, 1% Iron/Tin for resistance
Red Brass_____85%______15%_____37/100________Cheap_______?
Yellow Brass___75%______25%_____28/100________Cheap______?
Nickel_________0%_______0%_____22/100________Medium_____easy

28-ga yellow brass has arrived, I will cut it up and ship tomorrow, along with the red brass samples.

I still have lots of yellow brass free + shipping to anyone with a spot welder.

I don't think corrosion is a big issue for battery strips. Normally these would be protected from water and surface corrosion is really cosmetic as long as the welds are good.

Slotting is key for low resistance metals. I wonder if just shearing the strip would work, like with tin snips. The sides would touch but have a lot more resistance than a solid piece. Worth a try, since this is pretty easy. Mid-strip would still be hard. A Dremel tool with an abrasive disk works but would be really time consuming.

I have had good luck cutting through nickel strips when salvaging cells out of a cordless drill battery pack. I used a thin abrasive disc on a dremel. i am certain it would work well for cutting slots where they are needed.

I think I remember seeing somebody make a jig for the Dremel that holds it on arm that pivots. Works like a chop saw. The jig held the strip so the blade hits right in the center. Might be worth it if you want to do a large pack.

Shearing does help, not as much as slotting but it does make quite a difference. I just did it with a pair of scissors... Of course you need access to the end of the strip. Two thin parallel strips are the bees knees ( infinite slot) but super fiddly. The shape of the end of the slot makes a difference as well. Not that it's worth worrying about mostly, but sharp points lead to higher failure with some tabs blowing apart around the end of the slot (.1mm copper with too low a current and too long a pulse time) I'm wondering if I can punch a slot for the middluns, mich quicker than a dremmel. Maybe with a crappy wood chisel on a bit of thick aluminiumn or something- just musing.
Still haven't heard back from any of my emails about the copper alloys

My favorite cell (currently) is the 30Q, it seems to bridge the balance between capacity and amp-output (for me, at least). 5P would provide 75A peaks, and 18-Ah. 6P would be a beast, if it could fit your frame...

It seems that...the type of person who would go to the trouble of buying a spot-welder and building their own battery pack...they are not looking for a pack that outputs 20A. There are hundreds of those (on aliexpress), much cheaper than you could build yourself. They are either looking for a pack that fits a specific shape, or...they want high performance. Either way, I feel that brass parallel strips serve both of these "builder profiles".

spinningmagnets said:

My favorite cell (currently) is the 30Q, it seems to bridge the balance between capacity and amp-output (for me, at least). 5P would provide 75A peaks, and 18-Ah. 6P would be a beast, if it could fit your frame...

Click to expand...

Any experience with the LG HG2 ? Which one would you rather use in you build for that beast battery pack ? The 30Q or the HG2 ? Why ?

I have read good things about the HG2 cell from LG. I have not used any yet, but...I would not hesitate to buy a pack that was made from authentic LG-HG2 cells.

spinningmagnets said:

I have read good things about the HG2 cell from LG. I have not used any yet, but...I would not hesitate to buy a pack that was made from authentic LG-HG2 cells.

Click to expand...

I assume a lot of counterfeited HG2 cells are already in circulation. Right ?
I think there's even info/pics on the web on how to recognise fakes rewraps versus genuine HG2 cells.

I'd really love these HG2 cells (3000 mAh ! ; 20A!). The other ones i'm looking at are the Sony VTC4 (2100 mAh ; 30A !!!) which I tend to be attracted to even more!

Counterfeiters jump onto any new cell that is "hot". The PVC sleeves that heat-shrink onto the cells can be purchased to appear very professional and authentic. The only way to tell for sure is to buy several, and then load-test them to see how many amps make them warm, and measure the true Ah from a 2A drain to LVC and full re-charge.

Sony, Samsung, Panasonic, LG...if the cell is any good, someone will try to counterfeit it.

Check the 30q thread, ohbse tested hg2 and they fell short, well they're still good but 30q outperformed them in all cases.
K

kdog said:

Check the 30q thread, ohbse tested hg2 and they fell short, well they're still good but 30q outperformed them in all cases.
K

Click to expand...

Thanks for the tip.
Man I read the whole thread, I'm now more leaning towards the 30Q's than the HG2's.
Link for the 30Q thread : https://endless-sphere.com/forums/viewtopic.php?f=14&t=68556&hilit=30Q

Seem's like Samsumg are more conservative than LG in there testing.... HG2 might be rated 20A but would be outperformed by the 30Q, even at 20A in terms of Temps and longevity!?

I'd love to see both cells compared on same graph :

Graph 1 : Volts (and Temperature) versus mAh both for 30Q and HG2 on the same graph (at different discharge rate : 5A, 10A, 15A, 20A, 30A)
Graph 2 : Cycles versus mAh both for 30Q and HG2 on the same graph
Graph 3 : DC-IR versus Volts both for 30Q and HG2 on the same graph

I think it would help most of us choose between HG2 and 30Q.

A warm cell at 100F (38C) will likely perform at its peak abilities. When it reaches 140F (60C), I would say that this temperature is a reasonable maximum to allow.

What can a cell provide? 140F peak and 100F continuous will decide that. Everything else is marketing BS.

spinningmagnets said:

A warm cell at 100F (38C) will likely perform at its peak abilities. When it reaches 140F (60C), I would say that this temperature is a reasonable maximum to allow.

What can a cell provide? 140F peak and 100F continuous will decide that. Everything else is marketing BS.

Click to expand...

Are we talking air temperature within say a battery compartment, or the actual surface or internal temp of the cells?

I'd be interested to see what air temp i get inside my carbon nyx frame as my lipo cells warm up under load.

I'm kinda on hold right now on the brass spot welding. I tore my right rotator cuff (complete tear on one head and a partial on a second) Monday before last and can't really push down very well with my left arm. My elbow pretty much has to be stuck to my side at all times. Should have surgery in the next couple weeks so I should be back at it by spring.

Spinningmagnets I did get the brass by the way. Thanks and hope someone else carries on since I can not.

Being stuck on the bench sucks.....not my first time. No worries though, beats the alternative!

Tom

I did get the brass by the way. Thanks and hope someone else carries on since I cannot

Click to expand...

Several people have samples, and results should be posted soon. Even after that happens, there are plenty of experiments for you to post after you are healed up. Get well, my friend.

Well I have to say spot welding brass has got to be the most un-fun thing I have tried in the bike world so far. I just can't seem to find the right mix. Whether I try low volts and long weld time, medium volts and medium time or high volts low time it ends in failure. Last weld I did ended up blowing a hole in the end of a dead cell just to have it start bubbling out liquid stuff.

I've blown both ends of my tungsten tips and tried around 40 welds with the material Spinningmagnets sent me. I actually got a few to stick pretty good but the center of the weld vaporized the brass. They pulled apart realivily easily, definitely not finished weld material. I tried cleaning the metals first both battery and brass as well as trying in the raw state. I think I need some hints or advise from someone that has been able to make this work.

I feel like throwing in the towel at this point and sticking to easy to weld nickel but I won't.

Crap!

Tom

What kind of welder is that?

https://endless-sphere.com/forums/viewtopic.php?f=1&t=68521

It's a home built 800WS capacitor discharge welder. Link above pretty much says it all.

Tom

litespeed said:

https://endless-sphere.com/forums/viewtopic.php?f=1&t=68521
It's a home built 800WS capacitor discharge welder. Link above pretty much says it all.
Tom

Click to expand...

Got it.

I'm going to be trying shortly with a riba2233 welder. I also have a microwave oven transformer for testing once I get a timer.