This is all interesting.  I like the idea of getting more umph up to
the battery, and from there to my aux battery.  Keep us posted on the
failsafe considerations you are developing.  btw, what do you mean by "float."

Edward

At 04:41 PM 6/12/2010, David Beierl wrote:
Excellent point.  Something bad could definitely happen.  On this
>unit and I presume all of them, if you float the input the alternator
>will go to full output which with a small load might be a very high
>voltage.  The sense input draws 8-9 ma at 14.5v, so to failsafe it
>would need a suitable resistor across where the internal bus was
>cut.  I'll figure out what suitable is, but it shouldn't be critical.
>
>Now if the sense lead is *grounded* that will definitely drive the
>thing to full output.
>
>I haven't addressed the situation yet of the alternator output no
>longer driving the battery, but the sense input still connected there
>-- effectively it's the same as floating the input, since it will be
>immediately carried down to the loaded battery voltage.  Looks like
>the systematic solution to that would be to get the 30 terminals of
>the ECU/Fuel relays off the direct alternator wire and feed them from
>up forward somewhere, either the fuse/relay panel 30 terminal or
>direct from the battery.
>
>Another solution would be to use a diode to bridge the cut instead of
>a resistor.  That way the internal regulator voltage should never go
>more than a diode drop above the regulator set point.  Not ideal,
>would want a warning probably; but not instant disaster either.  And
>put a quarter-amp fuse in the sense lead, so it would blow if the
>lead was grounded.
>
>Have I missed anything?
>
>Yours,
>David