Robert M. Gary wrote:
: I have a 70amp alternator in my Mooney. I find that when I turn on the
: landing light, the voltage drops down to around 13.0 volts or less.
: During off the landing light brings it back to 14.5 volts. The Mooney
: Factory Service Center is telling me this is normal. They said Mooney
: didn't design the plane to fly around under the continuous load of the
: landing light.

: Opinions??

That isn't unusual to have reduced voltage output under load at low RPM.
What RPM brings it back up to 14v or so? Remember that even at 13v, you aren't
discharging the battery... it's not discharging until you're less than 12-12.5 or so.
It's just that the alternator isn't able to put out it's full voltage under that
current load. Depending on the state of charge of the battery, there's a 1-2v
difference between "appreciable current into battery" (i.e. charging), and
"appreciable current out of battery" (i.e. discharging).

-Cory

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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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