Please educate me on how "adaptive" regen works

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theothertom

Well-known member
Joined
Mar 20, 2017
Messages
364
Location
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Some EV's (Bolt, Leaf) have more than one regen mode whereby the amount of regen can be more or less aggressive. According to my limited understanding, regen is produced as the magnet in the electric motor (rotor) is turned by the wheel, and produces a force in opposite direction to the wheel turning (Flemings right hand rule ?), thus generating electricity and slowing the car down. What I don't understand is how this force can be varied. I guess I know just enough to be dangerous...can someone educate me? thanks
 
I'm not an expert, so my answer is only a guess.

The regen force depends on the amount of power generated which is a function of output voltage and current. The output current can be controlled by the amount of electrical resistance in the external circuit. So if the external circuit increased the resistance, the output power (i.e., the regen power) would be decreased.

An i3 driver is able to control the regen power from none to maximum by adjusting the position of the power pedal without a need for the various regen modes or steering wheel paddles used by other EV's. Some people criticize the i3 for not having regen modes or steering wheel paddles, but the only possible advantage that I could argue would be that if a driver wanted to be able to coast by lifting her foot completely off the power pedal rather than positioning the power pedal so that no regen or propulsive power is produced. I find this easy to do on an i3, so I don't miss regen modes or steering wheel paddles.
 
Nissan has been advertising an "e-Pedal" feature in the 2018+ Leaf that is basically how the i3's pedal works
https://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/e_Pedal.html

Easy driving using only the accelerator pedal

The e-Pedal allows the driver to start, accelerate, decelerate and stop using only the accelerator pedal.
.

Having driven a 2015 Leaf, and a Mercedes Benz B-Class, I can say I prefer the i3's regen system better. I also like that the i3's brake pedal works much like it does in a standard ICE BMW- pumping the hydraulic fluid to press on the brake pistons, and not much more. Many EVs have electromechanical brake boosters that makes the regen kick in when you press on the pedal, and the regular brakes kick in as you press further down on the pedal.

Like Art, I find coasting easy enough in the i3, as truly coasting rarely happens. Usually I need to trim/maintain my speed by applying a small amount of regen, or keep my speed from dragging by applying a small amount of power. if you need to coast with your foot off the pedal, you can use the gear selection switch to move into neutral. As the motor is permanently connected to the drive axle (there is no clutch), you can safely switch between "N" and "D" as you are moving along.
 
jadnashuanh said:
I think you'll find that on an ac induction motor, you can change the regen (the drag) by phase shifting the inputs.
That sounds intriguing. Can you go into more detail or link a website with more info?
 
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