DIY bus plating: electroplate, plus electroLESS

[spinningmagnets]

edit: the plating material of choice for me now is...Nickel. Also, in places where you want a weight savings, cost savings, and can tolerate a thicker mass of material for the same current-carrying ability as a certain dimension component of copper, aluminum busses are apparently a worthwhile material (see below). I have seen many examples of nickel-plated copper, but not yet any Ni-plated Al.

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This last year, I have become interested in using copper (or even brass) as bus-plates or at the very least, for the series connections between paralleled sub-packs at a minimum. The parallel connections between 4 cells in a 4P sub-pack will only need to carry the balancing current after a bulk-charge, so it would be much less than one amp, and that connection can be very thin. There is no issue using solid nickel strips in that application.

View attachment 2

But, for the series, it has to carry the full pack current, divided by the number of series connections between each P-group. The standard nickel "ladder" shaped ribbons that accomplish both parallel and series have one strip connecting every cell to each neighboring cell. For a 4P rectangular pack, there are four nickel ribbons connecting each P-group to the next one. If this is for a 40A pack, then each one of those ribbons have to carry a 10A occasional peak (10A per cell is common these days). Pure nickel isn't horrible for this, but...it's also not good.

View attachment 1

The pic above uses solder to connect a thin fuse-wire to the cell. I'm just including that pic to show the parallel connections can be small, and for performance, the series connection can be thick copper.

It only becomes an issue for very high-amp packs. If we look at what E-motorcycles are doing (with 300A systems, etc) they use copper flat bars that are pretty fat. Because there are so many issues with attaching the series connection directly across each cell, I am now a fan of configuring one series-bar across every two cells, which connect to the middle between two cells in the next P-group.

Regardless of pack-designing configurations, there is a growing interest in using copper for series connections. Its cheap and readily available. If you live in a dry climate, you will likely not be concerned about corrosion on the copper. This is the major benefit of using nickel in the common bus-strips, it is corrosion-resistant, and it spot-welds very fast and easy on an assembly line. As far as electrical performance its conductivity is about 25/100 compared to copper at 100/100. Plus, nickel is projected to become very expensive in 2018 if current trends continue.

If you don't want to use a plated part, but...you do want to have an electrical connection that is more conductive than nickel, but physically stiffer and more corrosion-resistant than copper...consider brass/red brass. it occupies a middle ground between pure nickel and pure copper. It is also cheap and readily available. Brass is made of copper with some zinc mixed-into it, and red brass has a little less zinc and more % of copper. Here are the electrical conductivity ratings (approximate, actual values will vary by purity and also the reporting website)

100__copper
61__aluminum
37__red brass
28__yellow brass (common brass)
27__zinc
22__nickel
15__tin

However, if you ARE concerned about corrosion on copper bus-bars (in the salty air near the beach), or...you want to make a product to sell to the public (which appreciates the good look and acceptable performance of a plated part), I thought this would be a great place to share any info on how to make plating as easy and cheap as possible.

Tesla uses thick copper busses that are nickel-plated (also high end cordless tools). Nickel, tin, and zinc all have a poor amount of conductivity (about 1/4th of copper), but...as long as its only a thin plating, the added resistance is negligible. I am interested in a DIY plating over copper...of zinc, tin, or a tin/zinc alloy for corrosion-resistance, and also to make the products look professional (zinc/tin alloy should be about the same conductivity as nickel).

Here's an awesome video showing a guy electroplating a steel part with a tin/zinc alloy in his garage, which polished-up at the end to a finish that is almost chrome-like. Electroplating only takes 3V plus a few chemicals, and it is easy and cheap.

https://www.youtube.com/watch?v=4c7Sw0BiPAo

[youtube]4c7Sw0BiPAo[/youtube]
As nice as this result is, I have also recently seen some "electroless" plated parts that looks very nice. I have known about "hot dipped" roofing-nails for quite some time. That is the cheapest way to coat steel roofing nails with zinc (and zinc is plentiful and cheap). The coating on those is dull and ugly, but it clearly works. I recently saw some electroless galvanized roofing nails that had a beautiful finish, so I know it is possible.

There's nothing wrong with DIY nickel-plating, so I welcome any info on that in this thread. However, I am most interested in DIY plating of copper with zinc, or a zinc/tin alloy...whether it is electro-plating, or electroless.

Below is a recent ES example of copper busses that would benefit from plating.

 

[Overclocker]

nickel plating is super easy. here i plated nickel directly onto a steel cog for aesthetics and rust resistance

make nickel acetate by dipping two nickel strips (i used 0.2mm nickel battery tabs) into Heinz distilled white vinegar, one strip positive, the other negative. use a 12v power supply or even better an iCharger using motor drive feature (use 12v 1a). run it for a few hours until the vinegar becomes pale green. the anode dissolves

to start plating clip your item to negative and a fresh piece of nickel as anode. set iCharger to 6v 1a.

 

[spinningmagnets]

That's awesome! That's exactly the type of hands-on info that everyone here can use.

 

[Overclocker]

they say a lower voltage yields better-looking results. i think i plated this at 7.0v

 

[12-C]

Nice job plating!

Spinningmagnetss, would aluminum not be a reasonable compromise and improvement over nickel?

 

[spinningmagnets]

Edit: due to the issue of galvanic corrosion seen in the link below, I now feel that pure nickel, or 70/30 copper/nickel is the best plating material.

Aluminum can be used to plate over copper or brass. However, it does have the tendency to oxidize, which creates a dull grey layer that is electrically resistive. If it had some benefit over zinc or tin, I would welcome it. The problem with raw copper as a bus material is that...in salty/humid air, it will develop an oxidized layer (green cancer). The purpose of plating is to eliminate that oxidation as an issue.

When you plate over a base material, the plating is very thin. That means that if the plating material has a conductivity ability that is equal-or-better than the 18650 shell steel, then the resistance to oxidation is the primary characteristic to be concerned about. Steel conductivity is 10/100 compared to copper at 100/100 IACS.

If you plate aluminum over copper, and it works well for you, no problem...continue with what you are doing. Zinc and Tin are common plating materials, and they are abundant enough that they are cheap now, and should continue to e cheap and abundant in our lifetime.

As far as conductivity compared to copper (even though plating is thin).

100/100 copper
61/100 aluminum
27/100 zinc <---------------
22/100 nickel
15/100 tin

compare this to oxidation sensitivity: After scanning several articles, the link below seems to have the best info in a concise manner.

http://www.pfonline.com/articles/corrosion-potential-of-zinc-alloys

The point of interest is that there is a trend of increasing the use of aluminum in automobile body panels, and the aluminum will benefit from a tin/zinc plating to resist corrosion.

Tin-Zinc alloys contain 70 to 90% tin with the balance being zinc. Although tin-zinc alloy deposits are not new, new technologies offer baths that are neutral and cyanide free. The deposit is ductile and maintains good solderability even after aging. Corrosion resistance equals or exceeds that of zinc-nickel alloys

Sooo...Zinc has slightly more conductivity, and Tin has slightly more oxidation resistance. The automotive industry has embraced an aluminum body-panel plating of 80% Tin with some zinc added. We care about both, but...in this application (copper busses with little exposure to harsh environments), I would like to suggest that conductivity is more important.

Therefore, if you don't have access to a plating of a 80/20 Tin/Zinc alloy, then...Zinc should be the plating material of choice...

If your biggest concern is only corrosion-resistance, consider nickel-plated copper.

 

[liveforphysics]

Zinc has many slick properties, but it's also a major galvanic potential.

 

[spinningmagnets]

If someone insisted that they needed some kind of plating over their copper busses, would nickel-plating be the best option?

 

[Hillhater]

If someone insisted that they needed some kind of plating over their copper busses, would nickel-plating be the best option?

That choice would depend on what they expected the plating to achieve.
Corrosion protection
Improved welding/soldering ability
Improved electrical conductivity
Etc
But if you are simply after corrosion protection, that would likely be compromised by spot welding etc, so wouldnt a traditional finishing coat of insulating lacquer be a simple viable option ? ( dip the whole pack in it even ?)

PS: as a corrosion protection, zinc has been commonly used (corregated iron sheeting, trailer chassis, boat fittings , etc etc) because due to its strong galvanic properties it does not have to cover the base material 100%.. Even partial coverage or the use of simple zinc anode blocks, will protect the base material for many years.
I am not sure if other metals offer the same level of protection from corrosion.

 

[12-C]

Spinningmagnets, thanks a pleasure to read all that.

In that conductivity series you listed, aluminum seems to be a much better performer (referring to it as a base metal and not for plating) than nickel,zinc but inferior to copper. What about using pure aluminum? There are various grades of aluminum, some that offer structural benefits, others that weld better etc. What is keeping aluminum from being the next best option and giving up on the complexities associated with copper spot welding?

Sorry if I'm side tracking, I agree it would be great if copper could be used BUT, with all the challenges maybe there is a better compromise. I just havent seen any mention on threads about aluminum as a candidate.

Thanks.

 

[spinningmagnets]

That's a reasonable suggestion. If I understand correctly, it is more resistant to corrosion from humid air (oxygen) than copper. And...although the instant reply around here is that copper is a better conductor than aluminum, how many of us are using pure 0.15mm thick nickel every day?

I guess if you were in a dry climate, raw aluminum would be cheap and easy to source for the series connections. Just make it thick enough that it doesn't get hot. If you ended up having any corrosion issues, you could plate the aluminum, or get plated copper to upgrade.

Aluminum is very galvanic (right next to zinc), and we have Luke to thank for warning us about that. It was not even on my radar screen before his post.

I guess the galvanic reaction when metal parts are near salt-water is one of the reasons nickel is so popular in industry. In the Navy I recall seeing Copper/Nickel nuts & bolts (CuNi)...now I know why.

edit: I just went back to see how nickel compares to copper on this galvanic scale, and I noticed that 70/30 copper/nickel was just as good as pure nickel. Hmmm...I suspect CuNi might be cheaper to plate copper with. I'll have to start researching this wonder material.

 

[liveforphysics]

Pure Nickel plating over copper is my favorite for most applications.

Nickel is a terrible conductor, but if all the interfaces are designed right it shouldn't matter due to how thin it is.

 

[Hillhater]

....... What is keeping aluminum from being the next best option and giving up on the complexities associated with copper spot welding? ..
Thanks.

Aluminium is a bigger problem for welding and soldering.
But Aluminium is the chouce for most major power distribution grids due to its conductivity, low weight, high strength, low cost, etc.

 

[spinningmagnets]

Thanks, Luke. I know how busy you are and I deeply appreciate any advice you are willing to share. You are one of the few people I read everything you have posted here (and some of the things you posted on emoto, etc)

edit:

Aluminium is the choice for most major power distribution grids due to its conductivity, low weight, high strength, low cost

I was surprised when I found out that most high-voltage power lines are braided raw aluminum. Most of the connections I have seen were some type of clamp, or crimp inside a sleeve, and I think spot-welding aluminum would be just as difficult as it is for copper. Its definitely interesting enough to keep in mind.

 

[liveforphysics]

Aluminum bussing is fast becoming the industry standard in EV power harnesses. Provided your interfaces to different metals involve gas tight weld joints (as seen above) it handily solves the galvanic drama and leaves you with just material fatigue sensitivity being higher than copper to deal with.

When in doubt, if you can get Nickel to adhere well to the surface of almost any metal it ends up improving joint integrity with respect to corrosion over time.

[moderator edit to fix link]

 

[Punx0r]

Galvanic corrosion is only an issue if your dissimilar metallic joint gets wet. For things like battery tab connections these things should be bone dry as a matter of course because if your battery is wet inside you've got much bigger problems than corrosion to the buss bars

Aluminium has a lot going for it: It's relatively inexpensive, easily formed & machined and its conductivity for its weight is much better than copper. So if size isn't an issue it has a lot going for it compared to copper. On the downside it does suffer from fatigue and creep, but these are mostly concerns applicable to wires and much less so to chunky buss bars.

 

[spinningmagnets]

There are plenty of youtubes on electroplating nickel, if you only watch one, this one is short, and I think it covers all the important bases.

To make the plating solution:
This guy runs 5V from a tiny wall-wart phone charger through two nickel welding rods that are resting in a glass jar of "distilled white vinegar" as a mild, cheap, and available acid (adding a tablespoon of salt as an electrolyte). Twice a day, alternate the pos and neg leads on the two nickel rods that are dissolving, so they dissolve evenly. This makes a usable nickel-acetate solution in about 48 hours. The nickel rods in the video are Forney brand, but any nickel rod will work.

There is nickel welding rod that does not say what its nickel content is. If you don't get something that is labelled 99% nickel, the other alloys in it will ruin the job.

https://www.youtube.com/watch?v=8dF2nKDAtEg

Here is is doing the nickel-plating. Making the Ni-Acetate is slow, but the actual plating process is very fast. He states it helps the warmer it is. Some industrial videos show the solution to be steaming hot, this guy gets fast results at around 110F / 43C. At the 9:00 minute mark, he shows a before and after with only 3-MINUTES of plating...sweet!

The black/negative lead is the one that makes a fizzle in the solution, and it needs to be connected to the part you want to be plated.

He claims the solution in the video was about three months old since the first time he made it, and and then used it, then...it just sat in his garage, so...apparently its not sensitive with a short expiration date.

https://www.youtube.com/watch?v=ju4uVhtkj2c

Here is a wonderful story. A certain Jewish scientist wanted to escape the Nazis in WWII, but he knew he would be searched, and his gold Nobel-prize medallion would be taken. He dissolved it into an acetate, and hid it in the chemistry lab. Years later, after the war, he returned and re-connect it ed the gold back into a solid. He took it to the Nobel Society, and they gladly re-assembly it from the original mould.