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ncc74656

copper vs aluminum for terminals/blocks

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copper can handle more current but if you up size the aluminum its just as good, right?

 

say you need a grounding block or a bus bar - the copper bar is quite a bit more money but its smaller, if you dont care about size an aluminum bar that is 30% or so larger can handle the same current; is there any reason to go copper over aluminum? 

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Copper is a better conductor so less material is needed versus aluminum in regards to resistance.

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yup. when running copper tho its hard to source pieces that are thick, easy to tap or thread.  could you stack slices, say a few layers of 1/4" plate and add that up to a 3/4 or so thick bar? braise them together or solder?  aluminum is much easier to find in blocks so thats why i was looking at using it.

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You can do that, but the point of contact is yet another point of resistance.  With that being said, you generally need 3 times the surface area of aluminum to copper.  In other words. all things other than thickness equal, a 1/4" copper bar will carry the same current (safely) as a 3/4" aluminum bar.

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Personally, I will avoid aluminum at all costs.  It corrodes much quicker from electrolysis and galvanic corrosion.  It's just not worth the trouble in an automotive environment.

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can copper be stacked? lets say i want to build for a max current of 500A. i can pretty easily get .25" copper but not any thicker. so if i had .25x1.25" that could carry around 300A. could i take two .25x1.25 and stack them to get 600A of current? and if so do i just bolt them together or solder or braise?  in an ideal world id like to have a .75" thick copper bar to drill and tap holes into for bolting ring terminals to. 

as for contact area - i cant seem to find any good data on contact patches. it does not make much sense to me that you have a thick bar with say 1/0 cable coming in and then a ring terminal with about 1/8 square inches of contact surface area on the ring terminals...  i dont have any of this installed yet so i cant do a voltage drop test. i want to get things right before i install (or as close as possible).

i built some aluminum battery terminals yesterday that seem to be working very well. i am picking up some of that paste that prevents corrosion. im concerned by the shrinkage of aluminum compared to copper so i guess ill find out if my bolts come loose in a couple weeks...  i wish i could find a 1X4X15" brick of copper, that would be perfect for what im doing. its just so much easier to find aluminum in those sizes and WAY cheaper. 

you mention copper can be much thinner - from what i have read and was told by people in the AC electrition field (no idea how DC changes things) aluminum must be upsized by about 25% to carry the same current as copper, the load isnt the major issue in their field but rather the terminal connection and how much more aluminum expands and shrinks by temperature.  i think thats right?

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Yes, you can stack them.  No need for brazing or soldering.  Just keep in mind, as I previously. stated any point of contact is a point of resistance and a possible failure.

Everything else you've typed is spot on.

BTW, I'm a journeyman electrician of 17 years and I have much experience in the 12VDC world as well.  I actually once use to build and re-manufacture alternators and other 12 and 24 volt electrical systems.

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nice. well im going to try my hand at making some copper terminals for my 2nd battery up front. im still going to coat the other al ones i made and just see how they get on.  i REALLY love the idea of threaded holes and i dont think i can do that with the copper but we will see... 

 

side question,  many amps and terminal blocks i see have set screws in them and it seems the terminals are al? i can scratch them and use vinnigar to test if its al right?  

is there a way to 'plate' al? like in a bath with a battery? i haven't googled this yet, first time i thought of it.

 

thanks.

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A lot of people like those bus bars, I’d personally wouldn’t use anything but copper. If you look at the average “big rig” battery setup, you would see how “I would do it”. Just seems like better connections with minimal chance of something falling onto the open bus bars and accidentally creating a short. 

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fair enough. im going to play with teh copper. im worried about tapping through sheets of copper plate, if a thread isnt just right... could split the plates apart.  its too bad i couldnt melt it down and pour it out into a different thickness bar :/

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If you must double up, drill all of your holes to fit on a single first, then use that for the pattern for the second. Don’t try to drill them together. 

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On the contrary.  Drill and tap them together.  It's the ONLY way to guarantee a perfect thread engagement.  If you do them separately, the threads will not align properly.   I've drilled and tapped thousands of buss bars.

In regards to aluminum on amps, the terminals are actually brass.  They are plated for corrosion resistance and it gives the look of aluminum.

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brass is below al for conductivity right? just that its such a small part interconnecting that brass works just fine?

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2 hours ago, Tirefryr said:

On the contrary.  Drill and tap them together.  It's the ONLY way to guarantee a perfect thread engagement.  If you do them separately, the threads will not align properly.   I've drilled and tapped thousands of buss bars.

In regards to aluminum on amps, the terminals are actually brass.  They are plated for corrosion resistance and it gives the look of aluminum.

Make a pattern with cheap metal. Drill your holes. Once correct, mate that to your expensive metal. Drill holes for test fit then tap together. This way you won’t screw up your expensive material and have to spend extra money.

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9 hours ago, ncc74656 said:

brass is below al for conductivity right? just that its such a small part interconnecting that brass works just fine?

You got it.  Just like most fuse and distribution blocks are made from brass.

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6 hours ago, Randal Johnson said:

Make a pattern with cheap metal. Drill your holes. Once correct, mate that to your expensive metal. Drill holes for test fit then tap together. This way you won’t screw up your expensive material and have to spend extra money.

That will work, but just as simple to drill and tap together.  It's especially helpful if you use a drill press.  Not for tapping of course.

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want to make sure im not deceiving myself.  if i have 3 wires on a long run, going into a fuse holder and then a single short wire going from the fuse to the battery, it should be able to handle the current with out significant voltage drop due to the short run and low resistance, right?  by the math the short run can but when paired with a long run behind it... i guess im not sure how to do the math when the wiring run changes size.

 

so three 00 over 11 feet into a single 00 for 4 inches or so to carry around 600A. that will work right?

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