Regen Braking Calculation?

[BrianG]

I am putting this in the CC forum because this is the most likely place that a CC rep may post a technical response.

We all know regen braking is used in our ESCs (well, most people know this, some just don't accept it - you know who you are). And we can presumably figure out the amount of kinetic energy a moving vehicle has using its speed, weight, and time to stop ((mass*speed^2)/time to stop). And we know braking efficiency (~35% ?) is not as high as during normal running.

But, is there a way to calculate if and how much actual battery charging is taking place?

Obviously, the voltage induced by braking has to exceed the battery voltage for regen charging to occur. Can we determine what that voltage is? And, am I to assume that if the induced voltage is NOT higher than the battery voltage that the energy is not being used to charge the battery, but is simply being absorbed by the motor/ESC (which would explain why motor braking makes components warmer)?

And then, am I correct when I say that the charge current is determined by the difference between the induced voltage and battery voltage, divided by various resistances (the output "impedance" of the motor, ESC copper, FETs, wiring, battery internal R, etc). Some of these can be assumed, some I have no idea.

Just curious.