This is my first post, so I do wish to apologize if it seems out of place or if comes too late. Since I seem to finally have found the keywords that answer the one peculiarity I completely don't understand about most electric cars, I'd like to ask a question (or maybe it's more like offering an opinion).
The one question about electric cars that has always been a complete mystery to me is why regenerative braking isn't seamlessly integrated with the brake pedal. After all, IMHO, regenerative brakes should be the primary brakes. I've also never understood why there is any need for regenerative braking to activate as soon as the accelerator is released – one should, after all, coast as much as one can.
Some background. My experience with electric vehicles comes from knowing how the accelerator and brake work in
these and
these.
In the trolleybus, it's very primitive: The accelerator pedal is the accelerator. If one takes the foot off the accelerator, the trolleybus coasts. The brake pedal is the brake, and it controls both regenerative braking and friction braking. In typical driving conditions,
friction brakes are not used at all. Usually, the trolleybus is driven in traffic and brought to a standstill using only regenerative braking. The friction brakes are only used to keep the vehicle still.
I'm saying "primitive" because the accelerator controls torque, not acceleration, and torque decreases when the power limit is reached. Integration between regenerative and friction braking is also accomplished in a very simple way: regenerative braking torque is applied proportionally to brake pedal deflection until the pedal is depressed halfway. If one depresses the brake pedal more than halfway, regenerative braking gradually cuts out while friction braking gradually activates (the transition is pretty much seamless).
In the tram, there is a hand controller. It basically has five modes:
- moving the controller forward proportionally controls acceleration (i.e. no matter what the weight and speed, acceleration at a specific position is always the same)
- there is a fixed forward position that maintains speed (basically, cruise control, applies some power so tram does not slow down)
- neutral – tram coasts
- there is a fixed backward position that maintains speed (applies some braking so tram does not increase speed downhill)
- moving the controller backwards proportionally controls deceleration (i.e. no matter what the weight and speed, deceleration at a specific position is always the same)
In the tram, which is more modern than the trolleybus, nobody cares about braking being regenerative or friction. As long as regenerative braking is available, it is used; if regenerative braking is unavailable or too much deceleration is required, friction brakes are applied. Nobody feels the need to separate friction brakes out or to apply regenerative braking when coasting.
So, basically, my question comes to this. Why doesn't lifting the foot off the accelerator simply equal coasting, why can't regenerative braking be the primary method of braking, and why aren't regenerative braking and friction braking seamlessly integrated in the brake pedal?