MS19087

MS19087

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Another thread was discussing the Plane Power feature that has an output to connect a panel light that illuminates when the alt stops producing power. Got me thinking - what is a better warning: a) a LOW Voltage (I have a Perihelion Design LV monitor) or b) an ALT OUT indicator; or c) BOTH?
A LV warning may give indication of a true failure, whereas the ALT OUT may be late notice. Comments? Thanks!
 
c) Both

The ALT OUT light would usually be a precursor to low voltage resulting from running on battery alone without a charging system. Having one would give you time to shed some loads etc. to maximize the remaining power in your system in the event of alternator failure.

A LOW VOLTS indicator means that things are going to stop soon, if they haven't already.

There could be some other causes of low voltage on a bus with the alt still good (bad connections, field bumped off etc). As long as you already have the LV indicator, why not take advantage of the ALT OUT output as well?
 
Actually a "low voltage" can detect when the alternator goes off line right away. Alternator puts out - what 14.7 Volts or so (depending on what regulator set point is). battery voltage is 12 something (I forget at the moment).

If low voltage detection is set to - say 13 V - then it will trip the moment alternator goes out. Then is the time to load shed, etc and get on the ground while yuo still have battery....
 
Richard is right, a properly designed low-voltage light will immediately illuminate when the alternator stops producing charging voltage. For my airplane, I chose to use a separate low-voltage light to monitor alternator output, instead of relying on the annunciator output from the alternator regulator. That way there's no chance for a regulator malfunction to both kill the alternator output and fail to illuminate the warning lamp. As an engineer, I like systems where the monitoring function is completely separate from the thing being monitored! Your mileage may vary.

mcb
 
I have the low voltage light from Van's; in combination with a digital volt meter, as well as an amp meter. Between these three, I get a very good indication of what's going on. My amp meter is wired as per Van's wiring schematic.

L.Adamson --- RV6A
 
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