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Re: urban legends? tire pressures

Had heard the one about concrete floors, hadn't heard the one about
metal ones.  Batteries undergo slow dicharge in idle conditions
anyway, have never been sure how the material underneath it was
supposed to affect it.  Had heard one explanation involving submarine
batteries(iused to work at a submarine yard), that the cold floor
caused diffeing concentrations in the electrolyte and the difference
in densities between the top and the bottom of the electrolyte next to
the plates caused a small current to flow, eventaully causing
discharge.  It's a story, anyway.  These were very large batteries,
though, like 4'-6' tall.

Most of your standard alternators require some current to flow through
the field  in order to generate AC current.  The only ones I can think
of that don't, use permanent magnets, like the old bicycle generators.
So yes, you have to have a non-flat battery in order to get current
out of one.  No push starts with a totally flat battery.  You probably
couldn't with the newer vehicles, you can't start them in gear anyway,
manual transmissions have interlocks to prevent it.  Moot point.  I
suppose with the old generators you could build up enough speed to get
enough current to light off the engine, but it would take a prolonged
push or a very long hill.  Have never tried it.  Being a DC machine,
the field iron has some residual magnetism and that can get things
started generating.  In fact, you're supposed to polarize the field
on VW generators after disconnecting the battery for any length of

On Tue, 2 Jun 1998 14:02:05 EDT, you wrote:

>some stories that guys at work have told me.
>true or not?
>1.  "don't put your battery on the ground (concrete, etc.) - that's the
>quickest way to kill it"
>why would this be true?
>2.  "don't put your battery on the metal floor (i.e. normal battery tray area)
>of the car, that'll kill it"
>why would that be true?
>3.  some guy was talking about "new cars" (a chevy truck, in particular) and
>said that the alternator won't recharge the battery if it's flat, it only
>"maintains" it.
>that i don't believe.
>and a question of my own:
>what tire pressures do any of you run on the front with stock wheels and
>tires.  17/18psi seems a bit low to me, even though there's not much weight

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