I am not going to give any classes on the value of regenerative braking in any and all electric vehicles and hybrids.
If you do not have regenerative braking, do not bother to build any kind of ev of hybrid.
It is the ability to regain the power of momentum so as to recover part of the power that was used to generate it to begin with.
This is the only advantage that an electric vehice has over an internal combustion drive relative to the efficient use of its energy.
The concept of regenerative braking is as simple as the drive itself
The problem only becomes an issue when one tries to do both simple tasks using the same system.
The problem is simplified when the regenerative braking is kept seperate from the drive
Then again even simpler when charging a seperate battery system.
The ideal electric or hybrid will use 2 seperate ballest systems that can be switched.
This does not mean that you need a larger ballast.
It simply means that whatever you have is divided to two seperate battery systems
One system will run the drive the other will be charged from the also seperate regenerative charging system.
The ideal point for size will be when the photo voltaic system on the roof of the vehicle combined with the regenerative charging will charge this bank at about the time that the system that is in use needs to be recharged. At this point you swap the systems using the appropiate switching system.
This type of system will have no limit in range. the only limit will be in speed of travel. This will be relative to the amount of power from the solar pv system and the efficiency of the drive.
Note this type of system will work much better in a large vehicle that can handle the weight of the batteries and has a very large area on the roof for solar panels.