My helm-mounted B&G Wind
instrument had the ability to display system voltage by pushing a button on the display head
. It read a tenth or two below what the Link showed due to voltage drop on the wires, but would give a good indication of the progress in charging
the house bank. Check to see if yours has that feature.
Alternators usually either work
or not, although there are some situations where the output can be diminished, like when they overheat.