Both traces start at take-off … but being at a new location I’d had to wait a good minute after switching on to get a GPS fix for the early/cold flight … and already the voltage was that bit lower, … but then plummeted immediately after starting the motors.
It rises, a bit, as the heat generated in the battery (by using it in flight) starts to warm it up … but it never reaches the trace of the flight when it was warm and sunny.
Now - you might think that they were charged differently, but at the far left you can see the coloured lines dropping very rapidly … I’ve zoomed on with the earliest values I can get on the cursor pop-up.
The only difference was for first flight (in the cold) the battery had been charged the evening before - whereas the later/warmer flight the battery had been charged perhaps an hour before.
I need to repeat this exercise - for this very purpose - rather than randomly bumping into it whilst looking for something on AirData.
And when I do it intentionally - I’ll hover at the end and take it down to 5% on each flight.
On a similar issue, I’ve always thought that the batteries seem to last longer when flying abroad in sunnier climbs, I have no hard evidence yet, but aim to look back now and find out.
Those graphs support that … it’s going to get to whatever voltage it deems as the % you set as critical earlier.
That’s only 10 minutes - and it’s obvious that the two graphs are getting closer … which makes sense. That’s why I’d like to do this intentionally and take it down to 5%. I should add a much warmer summer day to the same analysis, too. Even in the UK 15 isn’t hot … but chances are the impact 13 degs higher is less than the 13 degs between those two.
It doesn’t bode well for electric vehicles then. A bit like fossil fuel consumption figures being way off the mark, the battery range will be quoted when it’s warm and sunny with no heating or lighting on. Come winter you’d be lucky to get half the range they quote, unless technology changes of course.
As for me, I’m just going to fling a few more gallons of dead dinosaur in the tank.
