Copper strips instead of nickel?

F

flat tire

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Simple question, has anyone here used copper strips instead of nickel for increased current capacity and less voltage drop when spot-welding cells together? I found a scientific paper by the name of "'Spot welding' of thin copper sheets" authored by D F Dance and C Duncan but it's behind a paywall. Not sure why copper isn't being used, although I've considered of a few possible hangups:

--more power needed since copper has more thermal conductivity
--time-sensitive oxide removal could be necessary, or highly recommended for highest quality welds
--copper-stainless joining may have compatibility issues (assuming the battery casing is stainless). I know they can be tig / explosion welded though so hopefully this isn't a problem.
 
Yes, copper oxidizes, but since the points of contact will be fused with the battery or otherwise shielded, I don't think that's an issue once the pack is built. Besides, you can always nickel plate the copper if you're worried.
 
999zip999 said:
Every look at the Statue of Liberty. It's green.
Click to expand...

So you're saying snot might work better? Will the innertube goo conduct the downed power lines up your bike. . . ?

bike,diy,doityourself,handmade,light,design-58215bee7e8e35deb25e3db5ec83d4b9_h.jpg
 
flat tire said:
Yes, copper oxidizes, but since the points of contact will be fused with the battery or otherwise shielded, I don't think that's an issue once the pack is built. Besides, you can always nickel plate the copper if you're worried.
Click to expand...
There is a thing called (in my language) "cooper hemorrhage". It happened in 2 months laying on scooter seat, doing nothing, there is a hole in second picture. I think plating could solve it if you do not spot weld. Sourcing Nickel for plating right now, NI200 wire looks cheapest source. :D
View attachment 1
IMG_20150412_121031.resized.jpg
 
I'm saying if you use copper it will start to turn green in 4-8 months. Electricity just speeds it up. It also depends where you live. I live at the beach. Try it and get back to me.
 
Arent the cans nickel too? Or nickel plated? Then you weld nickel to nickel and don't get electrolysis corrosion.

I'm not sure. Maybe the nickel strip is simply cheaper and quality controls better through the spot welding.
 
Before going too far, I'd suggest figuring out how much voltage drop you get with a nickel strip and ask if it's worth going to copper. My guess is it won't be much, and likely not enough to be worth the added effort. The thermal and electrical conductivity of copper is about 4-5x greater than nickel, so it takes a lot more power to do the weld. On top of that, a lot of spot welder electrodes are made of copper, so you can have trouble with sticking electrodes.

For example: A 50mm long, 6mm wide, 0.15mm thick nickel strip has a resistance (lengthwise) of about 3.8mOhm. An identical size copper strip will be around 1mOhm.

I don't know what the internal resistance of the cells you're using is, but I suspect it will be significantly greater than the tabs.
 
Yeah, you're right. The IR of my batteries is a lot more than nickel strips. That must be why copper strips aren't used, barely any benefit with more potential issues.
 
spot welding copper can be a problem , the strip should have higher resistance then your electrodes and wires , thats the only way its going to heat up and weld .
 
I had this exact question, because SuPower sells "Pure Nickel strip tape" so its like Duct Tape, or Masking tape? Is it tape or is it metal? Is it metal with adhesive on one side, also known as "tape". Its the language barrier. I'm not about to email them tho. They lose my business for not being up to date or having atleast one dude with perfect ESL skills to review their website.
http://www.batterysupports.com/wires-plugs-scissors-pvc-c-53_56.html?page=2&sort=20a

I go here
https://www.bluesea.com/resources/108
and conductivity is waaaaay different. But I see the corrosion side of things. Dont want green stuff on the copper. Cant ya just solder the copper, or coat it with something?

But I see people all the time using copper strips on here, so I still dunno.

I will be doing like ~58V at 12.5Ah of used a123 m1a's.
Also I dunno if I can use the dimple "no tab weld" method with Supowers product.
 
I really don't think corrosion is a big problem with copper, unless you're exposing your connections to an environment with a lot of salt for a long time. The statue of liberty took something like 30 years to turn green, so not really the best comparison here. I use copper interconnects and they haven't even started turning green after years.

People on here do use copper connections, but I haven't seen anyone using welded copper tabs between cells. As I mentioned before, it's just not worth the effort when it's maybe 10% of the total pack resistance.
 
I'm going to "guess" that copper strips will work just fine...if...you live where it's very dry. If you live near the salty air in a beach community, I can state that the average person would be shocked at how rapidly copper will corrode away into a crumbly green sand. I spent four years in the Navy, with all of it being sea duty (rather than a desk job).

A dry crimp between two butt ends of wire can work well, but videos on YouTube from "marine" electricians (boats, not military) show that dry crimps (no solder) MUST have "liquid tape", or some similar sealant, or the copper strands will erode away rapidly, while the resistance of the connection will degrade almost daily.

If you don't live near salty air? Corrosion will happen slower, so your mileage may vary (YMMV).
 
interesting thread.
i have just become a test guinipig
PICT0094.JPGPICT0099.JPG

the key to welding copper is tungsten tipped(refractory) electrodes and a high power, short pulse.
you can actually see the tungsten tip light up like a cherry, creating the heat that makes the weld.
cells are still cool to touch immediately after, and any excess heat created is very quickly wicked away by the copper.

copper is way cheaper than nickel and can conduct much more current in a smaller conductor cross sectional area if required.

nickel coating copper is easy but may interfere with welding quality, as the nickel creates a higher resistance 'skin' that vapourises when the high power pulse, required to weld the copper, goes through it.

im hoping that keeping the copper clean(washed with isopropyl alcohol) , dry and salt residue free should prevent the green oxide from forming, just like any peice of copper thats lying around my house, but only time will tell .

if i do get issues, i guesse I always rip it off and try welding on something else.
 
err...yep :D
i just went and checked some copper i used on a samsung 20R pack serial connection back in 2013, still looks like the day it was done pretty much.
the only tinsy bit of corrosion to be found i would say is due to the plumbers flux I used back then in my wisdom(or lack there of)
I know better now....
PICT0130.JPGPICT0139.JPG
 
Aus.
i can see the sea from my house, but i would not say i get any salt spray here. :D also, they dont do the heinous road salting here, like i have seen done in europe.
iv shrink wrapped and sealed the packs also.
 
apart from resistance increase is there a risk of fire starting if using non coated copper to solder on 18650??
or other things to consider?
 
want to build said:
apart from resistance increase is there a risk of fire starting if using non coated copper to solder on 18650??
or other things to consider?
Click to expand...

id say resistance decrease if anything if using copper, but best not to solder anything directly to 18650. there are very good reasons not to
 
I used copper strips and solder for pack building for the last 5 years. I bought copper sheeting and cut strips to size. My system was pretty low power, never more than 20 amps on 20 ah 44 volt battery.

I live in rain forest climate in BC but did not let my batteries get wet.

I never had anything more than slight oxiding on the strips and never had a solder failure.

Just me 2 cents......
 
ridethelightning said:
want to build said:
apart from resistance increase is there a risk of fire starting if using non coated copper to solder on 18650??
or other things to consider?
Click to expand...

id say resistance decrease if anything if using copper, but best not to solder anything directly to 18650. there are very good reasons not to
Click to expand...

do you mean it spot weld is better than solder? is that the idea you are conveying?
 
what does the lose of energy looks like with nickel.
to have an idea .
one cm cube for 1meter cube? if you havea visual comparison so i can decide how much it weights in my decision

tx
 
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