# Copper pipe as bus bar



## DC Braveheart (Oct 12, 2008)

I've seen elsewhere the people have used flattened soft copper plumbing pipe instead of solid copper bar as a bus bar, for example, to connect batteries in a pack together or to connect the field coils on their motor - anyone got any opinions on going that route?

I was, for example, going to use a length of 2/0 welding cable for the field coil connections on my Warp 9. 2/0 cable is 0.3648" dia, which is a cross sectional area of 0.1047"^2. Copper pipe with an inside diameter of 0.545" and outside diameter of 0.62" has a copper cross sectional area of 0.0687"^2 ... so if I used 2 flatted pipes soldered together I'd have better than 2/0 - right?

Thanks


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## major (Apr 4, 2008)

DC Braveheart said:


> anyone got any opinions on going that route?


I don't like it. But used it once when I was in a pinch for repair on a hot tub heater. It will work. It is not the best alloy for electrical. And you work harden it when you flatten it, so it may be prone to fatigue failure later on. Soldering and insulation.....I think you're better off spending a few bucks and getting the right stuff for the job.


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## JRoque (Mar 9, 2010)

Hi. Major's got a good point there. You wouldn't want to use that material to bridge cells, etc as it can stress and crack. 

Where it might work - for a while, at least - is in making your own cable connector ends. Crimping flattened copper pipe at the end of your regular 2/0 cables might do. But if you look at a copper pipe that has been installed for a while, you'll see it turns dark/green from oxidation. That will ruin your connection and can lead to other issues elsewhere. You can get around that by dipping the crimped pipe in tin or something similar but by the time you've done that, your cheap pipe will be just as expensive as the real thing while still looking like a hack. Personally, I like the braided copper/tin bands for interconnects.

JR


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## DC Braveheart (Oct 12, 2008)

Thanks folks!


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## Ziggythewiz (May 16, 2010)

I used them for my rear pack, I heard from someone smarter they can take 800 amps (1/2" pipe) but didn't use em in front as they can't flex like 2/0 (VW bug, back pack is on 1 shelf, front split on 3). Saves $6-10 per connection (using floodies). No problems.


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## corbin (Apr 6, 2010)

Hey Stuart, I went with solid copper bus bars. I posted costs/details here on my website's blog:

http://www.corbinstreehouse.com/blog/2011/01/plug-bug-battery-bus-bars/

I don't like the idea of flattened copper pipe…seems sketchy.

corbin


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## DC Braveheart (Oct 12, 2008)

corbin said:


> Hey Stuart, I went with solid copper bus bars. I posted costs/details here on my website's blog:
> 
> http://www.corbinstreehouse.com/blog/2011/01/plug-bug-battery-bus-bars/
> 
> ...


Cool - I'll check them out (I found this site yesterday http://store.electrical-insulators-and-copper-ground-bars.com).

Thanks


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## Ziggythewiz (May 16, 2010)

One advantage bus bars have (whether solid or flattened pipe) is that most current flows on the outside of the conductor, so the same amount of material in a flat form factor will carry more current than a round wire.


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## DJBecker (Nov 3, 2010)

Ziggythewiz said:


> One advantage bus bars have (whether solid or flattened pipe) is that most current flows on the outside of the conductor, so the same amount of material in a flat form factor will carry more current than a round wire.


That's not correct.

At the frequencies that a motor controller runs at, the "skin effect" isn't significant for a typical size conductor.

The reason a flat bar can carry higher current is that the surface area is higher, and thus cooling is better.

Make certain that you know exactly what you are buying with copper. Most ground rods and even some "bus bars" are copper plated, not solid copper. And with the price of copper so high, there is probably zinc-copper alloys being passed off as pure copper.


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## Ziggythewiz (May 16, 2010)

Thanks for the correction, just something I had heard from other EVers.

I can't speak to limits from personal experience. I only push 400A accelerating and cruise around 100A. Haven't been able to really heat a conductor, 2/0 or 1/2" flattened pipe, though the 2/0s get warm.


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## RKM (Jun 9, 2008)

Stuart,

I used copper pipe, 3/4 flattened and doubled over on itself, in a few locations where cables would have been too bulky. Solid copper buss bar seemed too expensive, relatively inflexible and only available in quantities much greater than I needed.

So far so good.

Rob


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## DC Braveheart (Oct 12, 2008)

RKM said:


> Stuart,
> 
> I used copper pipe, 3/4 flattened and doubled over on itself, in a few locations where cables would have been too bulky. Solid copper buss bar seemed too expensive, relatively inflexible and only available in quantities much greater than I needed.
> 
> ...


Thanks Rob. The 2 places I was thinking of using it was for the connection on the motor between S1 and A1 and also in the junction box I'm designing which will contain my contactors and fuses for the connections to 2/0 going to the battery and to the controller. The link earlier in this thread seems to be a good source for solid bar so I'll probably go that way - but I'm mighty tempted to get some soft copper pipe and use that at least for testing right now. We'll see.

Thanks


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