Aluminum Chassis/Primary Wire 4

[Invoke]

Has anyone here used aluminum for chassis wiring or battery primary cabling? I was looking into the price/weight difference and I have been unable to even find any SGX, GXL, etc wiring with a stranded aluminum conductor instead of copper. Does anyone do this?

 

[IRstuff]

Why? There are critical downsides to using aluminum:
> Flammability
> Electromigration


TTFN
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[Comcokid]

Long time ago had a 79 Mazda GLC where one of the battery cables was aluminum. Eventually had to replace it as the wire pulled-out of the battery terminal clamp (used a top-post battery). Lead terminal was cast around the wire end, but aluminum doesn't adhere to lead like copper.

 

[GregLocock]

If you are trying to design a low mass system have a look at silver, it is surprisingly cost effective in some applications.

We never considered aluminium because of the oxidtaion and corrosion issues as we had sodium hydroxide solution all over the shop.

Cheers

Greg Locock


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[patprimmer]

Aluminium also quickly forms a non conductive oxide film on the surface on exposure to air.

As far as I know, they don't even use this on F! where they will spend thousands just to save a few grams.

Regards
Pat
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[Invoke]

Thanks, all. These replies were very helpful. I eventually found a supplier (

http://delphi.com/manufacturers/auto/ee/cables/cable-al/

) but from the information posted this doesn't seem like a good path. I was a little curious as to why SAE standards J1127 and J1128 never made mention of aluminum and it makes sense now.

 

[IRstuff]

One has to assume that the elimination of aluminum household wiring had ample justification, particularly in the current climate where copper wiring has become a target for thieves.

One place where aluminum still has some distinct advantage is in the wiring between the integrated circuit and its package leads. The annoying property of aluminum galling to other materials is actually an advantage when trying to ultrasonically weld aluminum to aluminum pads on the die and copper, gold, or kovar studs on the package.

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[patprimmer]

I thought aluminium wire also had some advantages in high power transmission lines in the power supply grid where overhead wires need a big span between towers. The savings in construction of the towers due to weight savings in the line can offset the other factors.

Regards
Pat
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[IRstuff]

Actually, there is almost never a weight savings, because the high-tension wires are actually mostly steel cable, since the spans are so long, neither copper nor aluminum can support their own weight; it's the steel that holds everything together

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[crerus75]

IIRC, the main problem with aluminum wiring in residential applications was the failure to apply antioxidant compound to the bare wire ends when installing into a breaker, receptacle, switch, etc. The thermal expansion/contraction cycle of aluminum allows for intermittent contact between the wire and its corresponding terminal. This air gap will grow a layer of aluminum oxide, which increases the electrical resistance of the junction and, consequently, the heat produced as current flows. After a few iterations you either get broken contact or a thermal runaway and fire. The antioxidant paste (NoAlox is one name that comes to mind) prevents a layer of oxide from forming by not allowing air to touch the bare wire.

Modern receptacles and fixtures often also have CuAl stamped or engraved on them, meaning they can also be used with aluminum wire. Their coefficient of thermal expansion matches that of the aluminum wires, which reduces the amount of air gap that forms upon heating. If properly installed (correct fixtures and antioxidant paste), aluminum wire can be safely used in residential settings. In fact, the main feed from the power pole into the house is often aluminum wire.

Contrast this to a typical automotive environment, where vibration, heat/cold cycles, corrosive environments (road salt), and (sometimes) exposed connections with no ability to retain antioxidant compounds make aluminum a non-starter.