...on how the VP-X is wired to sense voltage (V) and amps (A). Remember Amps <> Volts.
It sounds like the VP-X is wired to measure/report the state of charge or drain on the battery -- which is usually 0 when in-flight and everything is working correctly. It will indicate a discharge if the alternator drops offline.
Nominal system voltage (V) with the alternator running is ~14.3Vdc.
With the alternator offline, the system Voltage will drop to ~13.8Vdc and then continue to decrease over time, depending upon load, battery technology (lead acid, AGM, LiFePo, etc.) etc.
Do you have an aircraft electrical system schematic handy?
Retired Firmware Guy and Airplane Builder
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned
1998 RV-8 QB -- Started, Sold
Aided and abetted building a number of other RV's.
Last edited by bjdecker : 07-08-2019 at 05:34 PM.