Re: Automotive Circuit Protection - Part 2

[garwillis@msn.com (Garfield Willis)]

On Mon, 26 Jun 2000 12:00:54 -0400, "Peter D. Hipson"
<mail@darkstar.mv.com> wrote:

>Very true, which is why I never start the vehicle that is doing the
>jumping, since it will be the one that takes the hit when pulling the
>jumper cable(s), when the starter disengages, or there happens to be a bad
>connection! BTW, that amount of load dump may well indicate a (small)
>battery problem. 

Are yous guys old enough to remember when the conventional wisdom on
"correct procedure" for jump-starting "changed" to "NEVER have the host
vehicle running"?

Getting some good insights outta this thread now, especially the focus
on disconnecting the huge load of starter current from a high-reving &
output maxing ALT (it likely would be, since it would be trying to
charge up the badly discharged battery), not to mention that even IF
that didn't happen, another not-so-nice further dump occurs when you
disconnect the charging current to the one battery that's discharged,
when you disconnect the jumper cables. Both excellent observations.

In essense, an all around bad idea to have the host vehicle active, and
why.

In case someone might wonder, well if dumping the load from the starter
is potentially so lethal, why isn't it lethal to the vehicle itself
everytime you start it, forget the jumpering case. Reason is that at the
cranking rpms the ALT is turning, it's not putting out anything in that
case. So yeah, you most certainly do get a huge load change, but the ALT
isn't in the picture at that point, thankfully. Probly obvious, but just
thot I'd mention it anyhoo.

I too wondered about the battery condition, given the magnitude of the
transient Pat got, but assuming at least one of the batterys was in good
shape, it's hard to argue with measured experimental data. I spose there
might be another explanation, but it doesn't come to mind to me wee
brain at the moment.

Gar



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