I used my gf’s Mondeo for a comparison test, again using the cigarette lighter for a voltage measurement.
After starting, voltage hit 14.55 volts, and by the end of a 20 min run had settled to 14.2V running and 14.15V at idle.
Restarting was at 14.0V, but then climbed back to 14.3V, and then subsided again to 14.2/14.15V when stopped.
Headlights dropped the voltage by ~0.1V
Using headlights, front and rear heated screens and blower on maximum dropped to 13.6V, similar to my tests.
It looks like this car keeps a much higher charge all the time than mine, with my best voltage being less than the lowest normal voltage when the Mondeo is warmed up.
A 9000 from UK Saabs has been tested, and found to produce :
“Idling on the drive, with a reasonably charged battery, it was sitting at 14.05V. With the headlights on, it went down to 13.98V.”
Which is probably close to what mine does at startup.
Perhaps my current battery is very sensitive to inadequte charge, or something else is going on which I haven’t thought of yet…
Contacting the battery manufacturers is my next step…