YoshiMoshi
10 W
Has anyone ever tried using copper tape to build battery packs? Not sure if it would work. But I'm just realizing copper tape is a thing. You can get some thick copper strips to stick to cells this way.
Copper Tape?
- Thread starter YoshiMoshi
- Start date
You might look at JonesCG's posts about it. 
jonescg
100 MW
When used to adhere thin copper (0.07 mm) to nickel (0.15 mm) and then spot welding through the nickel-copper sandwich to the cell below, it increases the current carrying capacity of the connection. But the adhesive is just there to keep things in place.
Same here. Works well. It's a good way to get a little bit extra current capability, without shelling out for an expensive spot welder that can do .1mm copper
YoshiMoshi
10 W
I'm confused. So the adhesive glue does not conduct but people use it anyways?
We're not using the adhesive part of the copper tape, but rather the copper part. The adhesive is incidental.
Also, for the record, when you say "people use it," @jonescg and I are the only two that I know of who have used copper tape in a battery build. So don't take it as a tried-and-true method. But basically it's the copper-nickel spot welding technique, only with really really thin copper tape. Layer of nickel (or nickel-plated steel), and a piece of the copper tape, spot welded directly onto the cell so that the copper part is the part directly touching the cell. So the adhesive isn't doing the work of making the copper stick to the cell, the spot weld is what does it. In fact, when I do it, the adhesive burns and smokes off. But that doesn't matter, because once the weld is good, it's not going anywhere.
I don't know how jonescg did it, but I prepped my nickel strips by sticking the copper tape onto the nickel, then turning it over copper side against the cell for the spot well. I suppose if you stuck the tape to the cells, then laid the nickel over that for the spot weld, it would do the same thing.
I suppose what you're asking is, can copper tape by itself work as a good way to build packs? I'd say definitely no, because the adhesive isn't conductive as we've said, but also it's not gonna hold long term against the cell in a mobile application.
I have a roll of copper tape (plus a few other items), bought for cooling mod of my TSDZ2 motor, all of which I have never used (because my motor did not need it). Just dug it up and looked up the specs. It is 0.06mm thick, 20mm wide 10 meters long, weighs almost nothing (2.5 oz). The 0.06 mm thickness probably includes the adhesive so there's even less copper than the thickness suggests. I took a piece from the roll, lightly touched an ohm meter probes to both sides and got no reading (infinite). I lightly stuck the tape to a piece of aluminum, touched the probes to the aluminum and copper side of the tape and got a zero ohms reading. I was surprised the non conductive adhesive disappeared from the equation somehow. Still pondering how that works.
edit: I suppose the adhesive is easily squished aside?
edit: I suppose the adhesive is easily squished aside?
jonescg
100 MW
That's exactly how I did it. And yes, the adhesive is incidental - it smells a bit when you hit the spot welder.
Combination of both, I suppose
Spot welding copper thick enough to carry the current needed for most applications is nigh impossible with conventional equipment. Laser or ultrasonic welders would be needed for that.
Would this spot welder be considered conventional equipment? Read the comments, flux is needed to weld copper to copper.
YoshiMoshi
10 W
Thanks for the info
I think the 811H is a "super capacitor" welder?
Another question on copper, can the "cheap welders" on Amazon spot weld thin copper? I understand like people have said on here spot welding 0.1 mm copper is difficult and requires a good spot welder. However has anyone ever tried just spot welding thinner and thinner copper with a cheap welder until you got a good weld? Then you could just stack layers?
Like you could try 0.05 mm thick copper directly to a cell. If that doesn't work than go down to 0.04 mm and so on. It looks like 0.01 mm is about as thin as you will get. I would hope even the cheap welders could spot weld 0.01 mm copper? Likely even thicker? Than just layer as much as you need to to get your current rating.
Lots of data on Copper ampacity and knowledge on NEC 310 that has been used for a long time. Ampacity of nickel, not to well documented. So there's that too. I would feel better using copper in terms of trusting the ampacity values.
I think the 811H is a "super capacitor" welder?
Another question on copper, can the "cheap welders" on Amazon spot weld thin copper? I understand like people have said on here spot welding 0.1 mm copper is difficult and requires a good spot welder. However has anyone ever tried just spot welding thinner and thinner copper with a cheap welder until you got a good weld? Then you could just stack layers?
Like you could try 0.05 mm thick copper directly to a cell. If that doesn't work than go down to 0.04 mm and so on. It looks like 0.01 mm is about as thin as you will get. I would hope even the cheap welders could spot weld 0.01 mm copper? Likely even thicker? Than just layer as much as you need to to get your current rating.
Lots of data on Copper ampacity and knowledge on NEC 310 that has been used for a long time. Ampacity of nickel, not to well documented. So there's that too. I would feel better using copper in terms of trusting the ampacity values.
Stacking and welding thin copper tape does not sound like a good idea. Copper is soft. I can easily roll a sheet of 0.06 mm thick copper tape into a ball with my finger tips. I'd suspect the pressure required on the electrodes while spot welding will deform and puncture the thin copper tape. You should get a cheap spot welder and try it. I have a $12 spot welder from aliexpress that I'll do some experiments on copper tape with.
I think you are right. There are 6 of them reportedly.
BatteryMooch
10 kW
Actually, it is. Otherwise the tape could not be used for shielding purposes (lining enclosures, covering slits/openings, etc.), a popular application for these tapes. But the conductivity is low compared to the copper.
docw009
10 MW
There's enough energy from a high c-rate 3S Li-po cell to weld a copper sandwich, Just a matter of switching it in fast enough with a stack of MOSFET switches, no?.
This guy shows how he spot welded nickel/copper with something similar to this cheap spot welder. Based on that, I bought one, and it blew up during trials testing. So much for that,
I found out later this welder needs to be equipped with 10 MOSFETS. Mine only had five. There were some other mods needed too, Oh well. I don't need copper.
In your case, do you want to screw around adding surface mount components to a twenty dollar welder, or just spend $150 more for one that works.
Last edited:
YoshiMoshi
10 W
I think I have seen you on other forums. Could you please share what reference you use for ampacity ratings of nickel strip? Every table seems to have different numbers.
Yea I don't think I can spot weld copper nickel strip, and the ampacity of nickel seems to be shrouded in mystery. Copper is more well documented. So just looking at copper as a better alternative. Thought tape would get me around needing expensive spot welder.
BatteryMooch
10 kW
Sorry, I don’t use anyone’s tables. I test the strip myself for the particular application.
Everyone has different numbers because no one has defined what the heck their numbers mean.
The rated ampacity of a strip can vary wildly depending on what you want to base the rating on. Certain voltage drop? Certain temp rise? Melting point?And what about strip in open air versus under shrink wrap? Or that plus near warm cells? Or the difference between using two weld points versus six weld points at each end.
Length can matter too as short pieces can enjoy heat sinking from the ends but long pieces get no cooling from that in the middle. How to rate that?
But you can pretty much get an idea of what strip can handle how much current by looking at all the tables and averaging them. But a lot can depend on your priorities if they are specific. A certain voltage drop? A certain temp rise?
If you just want a basic idea of what the ratings might be, to roughly see what different lengths/widths/layer counts offer you, then find as many tables as you can and see what most say.
YoshiMoshi
10 W
I wanted to personally thank you for your cell testing. I've referenced your results many timesSorry, I don’t use anyone’s tables. I test the strip myself for the particular application.
Everyone has different numbers because no one has defined what the heck their numbers mean.
And what about strip in open air versus under shrink wrap? Or that plus near warm cells? Or the difference between using two weld points versus six weld points at each end.
Length can matter too as short pieces can enjoy heat sinking from the ends but long pieces get no cooling from that in the middle. How to rate that?
But you can pretty much get an idea of what strip can handle how much current by looking at all the tables and averaging them. But a lot can depend on your priorities if they are specific. A certain voltage drop? A certain temp rise?
If you just want a basic idea of what the ratings might be, to roughly see what different lengths/widths/layer counts offer you, then find as many tables as you can and see what most say.
I think we would want to ensure that the nickel strips don't exceed the rated maximum temperature of the cells since the cells are directly welded to the strips?
I think I'm at the point were obtaining experimental data on my own packs would be best. How exactly do you test your strips. Like what equipment?
I almost thinking using all the different tables as a guideline, put a temperature probe in my pack and measure the temp while the battery is in use and get a digital readout while in its intended use application.
NEC 310 lists ampacities for bare copper wire uninsulated. I'm tempted to just weld copper, and extrapolate NEC 310 table rating for bare wire, and see what cross sectional area of my copper strips is in terms of gauge and use this as an ampacity. People say NEC is the gold standard for copper and aluminum conductors. Only if there was one for nickel!
BatteryMooch
10 kW
I wanted to personally thank you for your cell testing. I've referenced your results many times
I’m glad my testing has been useful to you!Certainly that as it’s typically 75°C-80°C and that would be verrrry hot against everything under the wrap. Personally I wouldn’t want any part of the pack…cells, weld points, strip, wires, connectors…to ever exceed 60°C.
I use a power supply and electronic load so I can continuously run any amount of current through the wire or strip. I do both open air tests and under shrink wrap and fishpaper. In open air I paint the strip/wire flat black and use a thermal camera or “gun”. Under wrap/fishpaper I use a calibrated Fluke type-k thermocouple with a Fluke 52 II meter. You don’t need that kind of accuracy though..any thermocouple setup would probably be fine. Omega has some relatively affordable meters. Don’t buy cheap China or Amazon thermocouples though…junk.
I recommend not using thermistors as they are not consistent or accurate and are much, MUCH slower than small bead thermocouples. This slow response, can easily be 20 seconds, leads to readings that are too low for faster discharges.
NEC ratings are great, and conservative which is fantastic. But read the fine print. How many conductors, in open air or conduit…that makes a big difference. I think NEC rates for a 20°C temp rise too. Does that match your requirements? But as you said, nothing for nickel.
YoshiMoshi
10 W
Have you ever thought about being the one guy that can make things right, by posting ampacity tables from the data you collected from your experiments, and specifying what is meant by "optimal conductor" "good conductor", "poor conductor hot/warm", by actually specifying a temperature at different currents? You could even put in disclaimers that it's dependent on the operating conditions, and the table should only be provided for generic guidance, and testing in your operating conditions would be required to determine the exact current. This could be similar to your battery testing info. You could specify if it's in open air, cover by fish paper and so forth as well.
Certainly that as it’s typically 75°C-80°C and that would be verrrry hot against everything under the wrap. Personally I wouldn’t want any part of the pack…cells, weld points, strip, wires, connectors…to ever exceed 60°C.
I use a power supply and electronic load so I can continuously run any amount of current through the wire or strip. I do both open air tests and under shrink wrap and fishpaper. In open air I paint the strip/wire flat black and use a thermal camera or “gun”. Under wrap/fishpaper I use a calibrated Fluke type-k thermocouple with a Fluke 52 II meter. You don’t need that kind of accuracy though..any thermocouple setup would probably be fine. Omega has some relatively affordable meters. Don’t buy cheap China or Amazon thermocouples though…junk.
I recommend not using thermistors as they are not consistent or accurate and are much, MUCH slower than small bead thermocouples. This slow response, can easily be 20 seconds, leads to readings that are too low for faster discharges.
NEC ratings are great, and conservative which is fantastic. But read the fine print. How many conductors, in open air or conduit…that makes a big difference. I think NEC rates for a 20°C temp rise too. Does that match your requirements? But as you said, nothing for nickel.
So essentially when you do ampacity testing you "short" (but not really a short because there is a small resistance) a power supply with the lowest amount of potential difference across the strip that your power supply will go down to (0.1 V or 0.01 V) and steadily increase the current while monitoring the temperature?
I see that most cells state a maximum operating temperature of 65 C, then you want to add in a safety margin, so I think your 60 C is a good place to represent the maximum temperature of the strip.
You seem to have really nice equipment. I'm wondering if you have powerful "super capacitor" spot welder as well, and if so which one? I'm trying to evaluate if it's worth it or not over the cheap Amazon spot welders. All of the "super capacitor" spot welders appear to be from China and sold on Alli Express. People say don't buy cells off Alli, but if you want a "super capacitor" spot welder, Alli seems to be only supplier, or resellers on Ebay etc..
BatteryMooch
10 kW
I only have data from a small number of strip/sheet configurations and I’m not sure I can post any of the results due to client NDA’s for the work I did. Even if posted it would only benefit a few as one is for a 400A pack, another for a pulsed-1100A ultracap pack…often weird stuff like that.
A huge concern for me is the large number of questions I would get if I posted limited data. A lot of people would ask what happens if they had this slightly different or that a little longer or shorter or used double shrink wrap or four welds instead of six…literally hundreds of questions would come and I just don’t have the time. Most questions lead to multiple follow up questions too, about all sorts of things “now that they have my attention“.
If I tested strip/sheet/connections/etc. it would have to be a comprehensive suite of tests so almost no questions are left to ask. And that would take weeks to do…just no time.
I use a KWeld with two of its ultracap banks connected to a 60A power supply to keep the caps charged as I’m welding. Many have great results using verrrry good LiPo packs to power the welder too.
Cheap welders might be okay for doing one or two packs but I strongly recommend using a GOOD welder if doing more packs than that. Even for one or two packs it’s usually not worth the crappy welds just to save a few dollars on a pack IMO. Better to buy from a good pack builder who will do it right.
I use “constant-current” power supplies (two 60A models) that I can set to any current value. They will then auto-adjust their voltage to deliver that amount of current into whatever I’ve connected to it (if within its ratings).
YoshiMoshi
10 W
Hey I get, the whole never ending questions.
I was wondering if you ever had any chance or luck in determining the heat transfer coefficient for nickel strip to air under natural convection without forced air onto the nickel? Or if you were able to determine it from your experiments?
