Curious to best location for a shunt on a Garmin single alternator system and why?
On the
BATTERY.
That always tells me the battery state, with or without the alternator working.
In normal flight with alternator online, I will see +14 volts with 0 amps drawing from the battery. Good. I know the battery is fully charged and the alternator is carrying the full load. How many amps is the alternator producing? Simple. Turn off the alternator and read the current draw from the battery that was provided by the alternator. Want to see if your landing light is working? Turn on the switch and you'll see a momentary load on the battery before amps returns to zero.
Now...If the alternator fails in flight, I again see the discharge RATE of the battery. That helps me reduce the load if necessary by turning off high-draw items... extending the time I can stay flying. If the shunt had been wired to the alternator, amps would show zero. No useful info. I have a red alternator off light that tells me that. No value added.
Also, before starting the engine, I always see the discharge rate of the battery which is useful for reducing the loads while waiting.
One final good reason: I use the experimental EarthX battery which handles huge surges of current during start. It draws a lot of current from the alternator to bring the charge back to zero. I like to keep close watch on the EarthX voltage and amps... In fact, that battery requires a blinking status light to troubleshoot malfunctions. Putting the shunt on the battery gives me a way to constantly monitor volts AND amps.
My opinion: There is no advantage to putting the shunt on the alternator, while wiring it to the battery gives me constant power monitoring from before engine start until after engine shutdown.
Of course, this a lot like our "Primer Wars" debates...lots of opinions!