Plug in voltmeter

writes:


The problem is you need accuracy and cheap and accuracy don't go together.

I would be surprised if the accuracy of the existing voltmeters are much
better than about 2%, which would easily account for the difference.


I'll disagree. You don't need absolute accuracy. You want repeatability.
If it says 13.4vdc at cruise today, and it did yesterday; and tomorrow
it says 12.9v - Houston, we have a problem.

And unlike analog meters, a DVM can be within 2% and still dirt cheap.

But all you really need is a array of say 5 LEDs:

12.8v RED
12.9-13.5 YELLOW
13.6-14.4 GREEN
14.5-14.8 YELLOW
14.9 RED

{We can argue the setpoints...}

So it's Y before starting, G when running, maybe Y at high loads/low RPM,
etc.

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