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Silver Plated Buss bars

Ohms_Cousin

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Nov 6, 2020
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Been reading as many Bussbar threads here as possible.

I have read about Copper and Aluminum buss bars and the pros and cons of Al vs Cu.

Thing is, even if one were to use Cu buss bar, it still should be plated with Tin, or interestingly, silver (Ag). There are good reasons for plating, and given I am going to be making Bussbars for a marine environment I will be plating with Tin at a minimum. But Silver is interesting because it is the best electrical conductor.

So I got thinking about Al vs Cu Bussbars for my application. I would prefer to use Al because it is 1/3 the weight of Cu (boat application so weight is a thing) and because it is significantly cheaper as well. Whichever metal I choose for a Bussbar will need to be plated - Ie, use copper Bussbar and plate with Tin or use Aluminum Bussbar and plate with Tin.

Given that the metal used for a Bussbar (Copper or Aluminum) will be plated with Tin (or silver) does it matter what metal is used as the base metal of the Bussbar? How much of a difference is there between a Copper Bussbar plated with Tin Vs an Aluminum Bussbar plated with Tin?

And that brings up interesting thought - probably not economical but its interesting none the less. Could Aluminum Bussbar plated in Silver be as effective as a Copper Bussbar?

What i mean is, if one were to use a piece of Aluminum flat bar of the same dimensions as Copper Flat Bar BUT the Aluminum flat bar is plated in Silver - would it match the ampacity of the Copper Flat Bar?
 

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Last edited:
Skin effect occurs in conductors when an alternating current (AC) causes the current to concentrate near the surface of the conductor, rather than being evenly distributed throughout. This is caused by the interaction between the changing magnetic field generated by the AC and the conductor.

Here are some details about skin effect:

Skin depth
The depth at which the current density is about 37% of its value at the surface. Skin depth depends on the frequency of the current and the conductor's electrical and magnetic properties.

Frequency
The skin effect is minimal at low frequencies, like those found in direct current (DC) and low-frequency AC circuits. Higher frequencies amplify the skin effect.

Resistance
Skin effect increases the effective resistance of the electrical conductor as the frequency of the current increases.

Better conductors
The skin effect is more pronounced in better conductors.

Aluminum
Aluminum is commonly used in transmission lines because it's lighter than copper and has a greater skin depth.
 
Thanks for the info Tom. There is a LOT involved in all this.

What is your opinion on Silver Plating in general - better performance? Most likely not cost effective. But its interesting.
 
if one were to use a piece of Aluminum flat bar of the same dimensions as Copper Flat Bar BUT the Aluminum flat bar is plated in Silver - would it match the ampacity of the Copper Flat Bar?
No, even if an aluminum flat bar is plated with silver to match the dimensions of a copper flat bar, it will not have the same ampacity as the copper bar due to aluminum's inherently lower electrical conductivity compared to copper; the silver plating, while more conductive than aluminum, would not be thick enough to significantly offset this difference and match the copper's current carrying capacity.

Key points to consider:

Conductivity difference:
Copper has significantly higher electrical conductivity than aluminum, meaning it can carry more current with less resistance and heat generation for the same cross-sectional area.

Plating thickness:
A thin layer of silver plating on aluminum will not substantially increase its conductivity enough to match copper.

Important considerations:

Application:
While silver plating might be useful for specific applications where surface conductivity is critical, for high-current applications like busbars, using copper is generally the preferred choice due to its superior ampacity.
Cost and practicality:
Silver plating on aluminum could significantly increase the cost of the material without providing the necessary conductivity boost to match copper.
 
From the
No, even if an aluminum flat bar is plated with silver to match the dimensions of a copper flat bar, it will not have the same ampacity as the copper bar due to aluminum's inherently lower electrical conductivity compared to copper; the silver plating, while more conductive than aluminum, would not be thick enough to significantly offset this difference and match the copper's current carrying capacity.

Key points to consider:

Conductivity difference:
Copper has significantly higher electrical conductivity than aluminum, meaning it can carry more current with less resistance and heat generation for the same cross-sectional area.

Plating thickness:
A thin layer of silver plating on aluminum will not substantially increase its conductivity enough to match copper.

Important considerations:

Application:
While silver plating might be useful for specific applications where surface conductivity is critical, for high-current applications like busbars, using copper is generally the preferred choice due to its superior ampacity.
Cost and practicality:
Silver plating on aluminum could significantly increase the cost of the material without providing the necessary conductivity boost to match copper.
Agree with what you say.

Aluminum flat Bar can be upsized in dimms to match the ampacity of Copper. Aluminum will dissipate heat better, so that would be an advantage. However Aluminum will change dimensional size faster then Cu (expansion/contraction), so that's a down side.

I am thinking more along the lines of using Tin Plated Aluminum flat bar to connect the cells together so as to get the benefit of the Aluminum cell connectors (of whatever type they may be at the time one purchases) mating to Tin plated Aluminum flat bar. Ie, a lessor dissimilar metal to worry about and the issues this can bring. Will the Tin plating take away the Aluminum oxidization issues or will the various treatments still be needed?

Then to take that further, use Aluminum as a main Buss Bar that is sized appropriately for the ampacity chosen and then have that Bussbar fabricated to the design chosen and then have it Tin plated. Considering weight here as the batteries are spread out (boat).

I am looking at building our own Bussbars for a boat setup - there should be a good bit of Bussbar used on the total system so cost and weight are a concern. In the end it will cost what it costs as Bussbars are not the place to cut corners. But if I can make Aluminum work with a plating on it then it looks to be an interesting alternative to Copper.

I was specifically wondering when it comes to the Aluminum connector bars used to connect the cells together that if they were silver plated would it help in any beneficial way - my interest is to chase down every mv of resistance I can in the cell connections. I get some would say this is splitting hairs but I am interested in developing good work practice that brings the best results - every little bit adds to the sum total of the system. However from responses above it may not be a big enough advantage to warrant the cost. Its interesting though.
 
I had a boss try and use brass bars on a 1000A DC jet engine starter system. Suffice to say, it got very hot and I told them to just buy the damn copper bars...
 
OK, so if one wants to get the lowest resistance possible between cell connections would silver plated copper buss bars be very useful or just useful - ie, is thier any great benefit that warrants this effort/cost? I expect there would be some improvement but would it be enough to justify the effort?
 
If you want to lower resistance try to get the proper contact pressure. Many bus bar connections are too loose. Resistance lowers dramatically up till about 4,000 - 5,000 psi for copper to copper connections.
 
Skin effect and plating only matters at RF, where skin depth is in microns.
At 60 Hz, skin depth is 8mm, so only very fat cables show any issue.
e.g. high tension lines having steel core for strength, aluminum strands on the outside.

Plating matters to prevent corrosion and native oxide (especially for aluminum, which instantly grows a non-conductive oxide on exposure to oxygen.)

Plating matters for dissimilar metals. Tin plated aluminum in contact with copper is OK. Bare copper and bare aluminum is undesirable. Maybe we see tin plated copper on bare aluminum, might be OK with surface prep and goop. PG&E appears to use crimp plated connectors on bare aluminum. The crimping process breaks through oxide and seals.

In a corrosive environment like boating, even more so where there is salt spray, I would want to avoid aluminum. If entirely sealed (e.g. aluminum inside a lithium cell) it would be OK. I think tin plated aluminum would be subject to corrosion getting under the plating. Maybe if heavily gooped it would survive.

I favor all copper. My breaker panels and breakers unfortunately have aluminum lugs. But at least I'm on dry land.
 
Skin effect and plating only matters at RF, where skin depth is in microns.
At 60 Hz, skin depth is 8mm, so only very fat cables show any issue.
e.g. high tension lines having steel core for strength, aluminum strands on the outside.

Plating matters to prevent corrosion and native oxide (especially for aluminum, which instantly grows a non-conductive oxide on exposure to oxygen.)

Plating matters for dissimilar metals. Tin plated aluminum in contact with copper is OK. Bare copper and bare aluminum is undesirable. Maybe we see tin plated copper on bare aluminum, might be OK with surface prep and goop. PG&E appears to use crimp plated connectors on bare aluminum. The crimping process breaks through oxide and seals.

In a corrosive environment like boating, even more so where there is salt spray, I would want to avoid aluminum. If entirely sealed (e.g. aluminum inside a lithium cell) it would be OK. I think tin plated aluminum would be subject to corrosion getting under the plating. Maybe if heavily gooped it would survive.

I favor all copper. My breaker panels and breakers unfortunately have aluminum lugs. But at least I'm on dry land.
Some interesting thoughts.

With marine its important to use tinned wire, so a tinned bussbar is probably beneficial in that environment.
 
Thanks for the info Tom. There is a LOT involved in all this.

What is your opinion on Silver Plating in general - better performance? Most likely not cost effective. But its interesting.
My experience: Silver gets coated with something black (silver oxide?) in humid environment.
 
I'm not sure you can directly plate silver into aluminum.

My vote is tin plated copper, coated with a decent layer of oil or grease to keep oxygen away.
 
Seems like Tin plated copper is the way to go. I am still inquisitive about Silver plating copper though - it would be interesting to see a test - copper Bussbar that is Tin Plated and its resistance measured in millivolts - then the same setup tested the exact same way but this time using Copper Bussbar Silver plated and then measure its resistance in millivolts. As for silver oxidizing I am sure there is something that could be smeared onto the silver to stop the oxidation.
 
Seems like Tin plated copper is the way to go. I am still inquisitive about Silver plating copper though - it would be interesting to see a test - copper Bussbar that is Tin Plated and its resistance measured in millivolts - then the same setup tested the exact same way but this time using Copper Bussbar Silver plated and then measure its resistance in millivolts. As for silver oxidizing I am sure there is something that could be smeared onto the silver to stop the oxidation.
This talks also about sulfur in the air.
 
I only use copper and nickel plate it.

This large busbar is 4 foot long, copper with nickel plating. Bolts are stainless carriage bolts, I cold head the square hole using the shop press. The busbar from Class T to large busbar is copper and nickel plated.

1728485934749.png
 
While it is an interesting conversation to have, if you spend this much time on this topic, you will never finish a system.
All of the different iterations of this issue are well understood and have already been discovered. You're not going to discover some unknown quality in plating and base substrates.

You need to learn how to search Google. All of my replies above were simple cut and paste from Google searches.
 
While it is an interesting conversation to have, if you spend this much time on this topic, you will never finish a system.
All of the different iterations of this issue are well understood and have already been discovered. You're not going to discover some unknown quality in plating and base substrates.

You need to learn how to search Google. All of my replies above were simple cut and paste from Google searches.
Tom,

Thank you for your responses. Rather ask here from people with real world experience then a Google search. If it bothers you so much why do you bother replying?

I am drilling down into bussbars to learn the absolute best way to deploy a battery system - bussbars are super critical to the success or failure of a battery system over time.

I need to install batteries in a boat - the boat is undergoing a rebuild - so lots of time to figure out battery systems. So your assumption of never having a finished system is wrong - as a lot of assumptions are. I am getting down into the weeds to figure out the tiniest details - and chasing down resistance in the batteries is a big issue that is important to both understand how the resistance is getting up in the first place and how to resolve this problem. My assumption (probably incorrect) is that a lot of people gloss over the bussbars and just how important they are. I want to figure out how to get the resistance in bussbars as low as they can be. Just good installation practice.
 

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