The future of electric cars and hybrids – aluminum or copper wire?


The new Audi TT moved its battery to the rear and connects it to the engine compartment with aluminum battery cables.  The marketing materials in the press release said using aluminum wire reduced weight and moving the battery to the rear improves the weight distribution front-rear.  Normal cars use copper wire for the battery.  This got me thinking – are there any other possible benefits/drawbacks of moving the battery to the rear and using aluminum instead of copper?

First, are their claims true?  Yes.  Most cars are front engined and moving it to the rear balances the car better.  the heavy battery also takes up space.  Moving it to the rear also frees up underhood space.  European pedestrian impact laws dictate a minimum space between the hood and any hard spots and this requirement has hit sports cars especially hard by raising their hoods and making the lose their low sporty hoods.

One downside is that it takes up rear room and it requires some kind of access compartment to seal it off from the cabin.  This is because batteries contain lead and acid which can give off toxic fumes. I hope that the trunk is not electrically actuated or has an easy to find manual release because if the battery dies, how are you going to open the trunk to get access to charge the battery?  Before you say who would implement such a stupid design, Porsche sports cars are well known for this.  The trunk cannot be opened without electricity and the manual release is behind the wheel well plastic which requires wheel removal and trim removal.  The trick is that you have to connect a special fuse in the fusebox to a charger to get enough juice to pop the trunk.  German engineering, lol.

Another downside is that the battery must transmit the juice all the way to the engine compartment instead of just a short distance from the battery to the starter.  I’m just using the starter as an example because cold engine starts are  one of the most strenuous things the battery will be subjected to.  There’s a reason batteries have CCA or cold cranking amps stamped on them and not “turn on the radio” amps.

This brings me to the reason I typed aluminum or copper wire in the title.  Which do hybrids and EV use? I’m not sure but I just got a great idea for my next article, lol.  Could switching to aluminum wires save weight and increase fuel economy?  Since so much energy flows through the electrical system on a hybrid or EV, would it make a difference?

Aluminum saves weight but copper prices have been high recently and most importantly, copper has a lower resistivity than aluminum!  I realize the Audi TT will save a few pounds and gain a tiny bit of fuel economy by that weight loss with aluminum battery cables.  However, the greater resistance of aluminum also wastes electricity which will result in a tiny (really tiny) loss of fuel economy and moving the battery to the rear will cause a voltage drop which might require the use of a larger (and heavier) battery.  The actual cables have to be thicker but because aluminum is lighter than copper, it saves 6 pounds according to Audi.

I assume the engineers have done the math and the benefits outweigh the drawbacks.  That said, are aluminum battery cables in the marketing brochure really a selling point?  Does the average car buyer care, know the different, or will ever see the battery cables?

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