Effeciency of regenerative braking

[The_Thinker]

I am just curious, but what is the average efficiency of Regenerative braking? As in... How much of the kinetic energy are they able to convert back to electrical?

 

[Mech_Engineer]

A quick search on Google yielded:

It is estimated that regenerative braking systems currently see 31.3% efficiency; however, the actual efficiency depends on numerous factors, such as the state of charge of the battery, how many wheels are equipped to use the regenerative braking system, and whether the topology used is parallel or serial in nature.