Why do we think the cap is steel?  Nickel is a better choice if you don't
look at cost.  Or a bonded bimetal.

There are probably ways to do a good job of this.  I have cooking pots that
are aluminum bonded to stainless steel.   Like wise copper to stainless.  I
have used silver bonded to brass (admittedly not a bad combination as we
might assume aluminum to be).  Anyway, if you get a good fusion bond then
you can stop worrying about the dissimilar metals bit because no moisture
can be involved.

Earlier this year someone mentioned that the conductivity of stainless is
far less than that of nickel, however the conductivity of wire is expressed
as cross section and length.  That means you can have a connection with a
enough cross section and very short length and the resistance does not sum
up to anything worth worrying about.

One thing I have not sorted out yet - the choices of electrode materials in
Li ion batteries.  I have heard that it doesn't matter that one is copper
and the other aluminum - could be two of copper, or presumable two of
aluminum, or two of nickel.  Given what can go awry with stacks of thin
aluminum electrodes clamped together with a terminal - what makes that a
common choice?

On Fri, Sep 19, 2014 at 12:39 PM, Lee Hart via EV <ev@lists.evdl.org> wrote:

> via EV wrote:
>
>> So my basic question is if the cell is already Al to Steel
>> internally, might it be better to go Al to Steel to Al (that last Al
>> being my intercell connectors) than to do Al to Steel to Cu (which
>> would be copper intercell connectors)?
>>
>
> What little I know about metallurgy tells me that attaching steel to
> aluminum is a bad idea. Maybe it can be done right by experts with special
> techniques. Others who are knowledgeable about such things may have more
> data with references.
>
> But it's something that would normally be avoided. Just because the
> Chinese did it does not make it good practice (they favor cheap, not good).
> Certainly, for connections outside the cell in the "real world" of water,
> oxygen, dirt, corrosion, etc. I would definitely avoid it.
>
> If you insist on doing this anyway, then you should plan to measure the
> actual resistance of each and every connection.
> --
> If you would not be forgotten
> When your body's dead and rotten
> Then write of great deeds worth the reading
> Or do these great deeds, worth repeating.
>         -- Ben Franklin, from Poor Richard's Almanac
> --
> Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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>


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