David Lesher wrote:

There's an easy test while in flight. Turn on some load - the landing
lights will do nicely. The zero-center battery gauge should stay
the same, ...

Actually, there is a short deflection to the right, lasting less than a second, after
which the needle centers again. I use this test during runup to simultaneously check
the ammeter and the lights.

George Patterson
If you don't tell lies, you never have to remember what you said.