ah, I was tired, I was thinking of 50mph, which is about 25m/s

Force = mass * acceleration => a = f / m

Force * speed = power => f = p / s

so a = (p / s) / m => a = p / (s * m)

a = 50000 / (25 * 1500) = 1.3m/s^2

does that make sense? I'll correct my comment above if so.

thanks

@davesul

Thanks Paul for explaining your method.

I looked at it a bit differently - based on Kinetic Energy of the vehicle.

Below are examples of deceleration values for 50 kW power, reflecting the variation for different speed drops compared to a starting speed of 50 km/h.

For speed = 50km/h, ie 13.9m/s, and mass = 1500 kg, the vehicle Kinetic energy (KE) : 0.5*m*v^2 = 144676 J, ie about 145 kJ. Then since W= J/s, this can be expressed as KE = 145 kW.s

Then for dropping to 45 km/h, the corresponding new KE is 117 kW.s and so the regen energy is the difference of the two KE values - about 28 kW.s. At a regen power of 50 kW, this corresponds to about 0.56 seconds for the energy to be absorbed by the regen system. The corresponding deceleration is then about 2.5 m/s^2.

For speed dropping to 30 km/h from 50 km/h, the corresponding new KE is 52 kW.s, the change of KE is about 93 kW.s and at 50 kW level this takes about 1.85 seconds with corresponding deceleration of 3 m/s^2.

To actually come to a standstill, the regen system would have to absorb all the original KE of 145 kWs, taking 2.9 seconds at 50 kW rate with deceleration of 4.8 m/s^2.