Current generation while coasting

Gathering data from an highway trip full of ups and downs, here's the chart of the current generated when the car is coasting (running without pressing the accelerator or the brake pedal).

Observations:

Beside some spurious samples in the transition phases, a clear behavior emerges.
Under 12 km/h there's no energy recovery, instead crawling consumes some energy also.
The energy recovered grows along speed until a little less than 60 km/h, afterwards it decrease a little and then it's steady until 100 km/h where it decreases again.

I suspect that every car model has its own characteristic curve.