Frank Ch. Eigler wrote:
writes:

My EDM700 (Arrow 200) has shown 13.5-13.7 in flight for a couple of
years. It recently dropped to 12.1, which I've interpreted to mean
the
4-year old battery is shot. [...]

If the voltage drops in flight, I would suspect the alternator
system(s) rather than the battery.


I agree. I've had several charging system problems over the years
and 12.1V is what I see whenever my alternator goes offline. That's
equal to a charged battery (~12.6V) minus the load from a few radios
and accessories.

John Galban=====N4BQ (PA28-180)