In rec.aviation.owning Robert M. Gary wrote:
: When I turn on a lot of accessories on my Mooney F '76 I can drop the
: bus voltage down to around 13.6. My A&P says 13.6 is normal with
: accessories on. Does this sound right?

Don't forget that the charging voltage for a lead-acid battery is *supposed*
to be modified by ambient temperature, with a higher voltage at lower temps.
This is commonly done with a thermistor in the voltage regulator. Even
the mechanical (vibrating relay) regulator in my 1977 Datsun has temperature
compensation.

That said, 13.6V is probably OK. If you check the volts on the battery
terminals you'll probably get a little more than the 13.6V on the avionics
bus, because the battery is wired to the alternator with heavier wires.
--
Aaron C.