> > > Measure the current.  It will flow one way as an indicator of engine
> > > start-up, and the other way until the battery is re-charged from the
> > > effort...
> >
> >         Hmm, now that's a good idea, only problem I can see if
> you'd have
> to build
> > your shunt such that it could pass the hundred or more amps
> needed during
> > starting, without suffering a large drop. TTYL
>
> Just tap an opamp/comparator across a small portion of the battery
> conductor. Design so that the differential signal will be enough to
> consistently switch the comparator one way or t'other.

        That could get VERY tricky in an automotive environment for two reasons:
1. there is ALOT of noise in care, filtering all that out is difficult.
2. There is a HUGE difference in the amount of currently flowing through
that conductor. During starting there can be hundreds of amps. During
operation there can be almost nothing flowing (assuming a fully charged
battery).

Note I'm not saying it's impossible or not worth the effort, I'm just
mentioning the problems I see in doing it. TTYL

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