How much current can you get from speed?
In the following graph:
- speed is in blue, left vertical axis
- RPMs in red, right axis, useful to check when the engine stops beeing dragged.
- change current in yellow, left axis, negative values are indicative of recharge.
I drove a straigh, plain road up to 76 km/h and then I left the accelerator pedal alone, to let the car loose speed until 46 km/h (see the blue line decreasing over time)
The engine continued to spin without burning any fuel, then at 66 km/h it stopped (see the sudden break in the red line).
Charging current is not steady, it follows the speed, but not linearly (check the yellow line, lower values mean higher charge).
A graph of current values by speed shows a pattern:
The higher recharge effect is at 66 km/h with 24A.
That is precisely the speed where the engine stopped, but neighbouring values vary widely.
The slope returns to a linear behavior at 62 km/h with 22A.
So, if you're going to drive down a hill and you want to maximize your recharge, it's better to drive at 60 km/h rather than 70.