REFLECTOR: Using the starter supply(+) wire as a charge wire

[Sid Knox]

Hi Terry,

> I have a Grand Rapids EFIS and engine monitor system.  The EFIS gives
> digital voltage readout of the V that it is sensing in its own input power
> line.  Additionally there are 3 available power inputs so I will have a 
> 2nd
> and even a 3rd Voltage taps elsewhere (like a hot batt bus) if I want it 
> at
> the expense of using up my user defined auxiliary inputs.

Just a comment about voltage sensing...
Here is a "thought experiment":  Take a hand-held, reasonably accurate DVM 
and attach the (-) lead to the (-) battery post.  With the normal electrical 
and electronic stuff powered on and operating (engine not running), take the 
(+) DVM lead and probe various +12 V points in the plane...engine 
compartment, nose compartment, whatever you can reach under the instrument 
panel,  etc. and record on paper the various readings.  When you examine the 
data you will most likely find variations as much as a Volt or more due to 
the normal wiring losses (or not-so-normal losses if mistakes have been made 
in the design/wiring of the system).  Now,  instead of leaving the DVM (-) 
connected to the battery, take it around with you and when you find a place 
to make a measurement, use the nearest GND point for the (-) DVM lead.  You 
will likely get different values than the first time around because there 
are losses in the GND wiring also.  Want still different numbers?  Do the 
same measurements with the engine running and the alternator pumping current 
into the system.  Voltages near the alternator will higher than those 
further away.
Ok, so what is my point?  Simply be aware that when your EFIS reads 12.75 
Volts and assuming it is reasonably accurate, that there is 12.75 Volts at 
the input to the EFIS (referenced to whatever GND the EFIS is using) and 
there will probably be more or less somewhere else in the system... at the 
battery for example.

> I will wire the B lead of the alternator over to the now dead Skytec input
> lug and use it like a terminal to the #2 starter (+) wire in the utility
> duct and will now carry juice back to master relay and from there to 
> normal
> bus distribution.  .

I do not understand this  "... to the now dead Skytec input lug ..."
How can it be dead and still supply starter current?