Regeneration and one-pedal driving

[BrianStanier]

I've just come back from a Rex test drive and remain impressed with the t3. But one question the dealer and the on-line chat have been unable to resolve definitively is what happens to regeneration and the ability to almost one-pedal drive when the battery is 100% charged. In our Leaf with much less aggressive regeneration the pedal feel changes as regeneration is lost but not enough to be a concern. The Rex I drove was not fully charged so I couldn't test this myself. Has anyone been able to experience the feel at 100% or have an answer?

 

[Waitingi3]

Just guessing here - since BMW only makes 18KWh available from the batteries 22KWh, then 100% as you see it is not actually a full charge of the battery. Hopefully, any regen when you consider the battery fully charged can be absorbed within the BMW designed safety buffer.

Look forward to hearing the reality of it soon!

 

[TomMoloughney]

This exact question was asked to Jacob Harb (North American electric vehicle manager for BMW) at a private event for BMW ActiveE lessees. He said that the regen will be the same even when the car is fully charged. The person asking the question then asked again because he didn't think Jacob really understood what he was asking and Jose Guerrero, BMW i3 product manager stepped in and said the same thing, that the regenerative braking will feel the same even if the car is 100% charged. Others chimed in to make sure he knew exactly what they were referring to and they offered the situation where you start the day 100% charged and begin going down a steep hill, will the car release the regen because it's fully charged and his answer was "No, it will still feel the same with the regen as strong as it is when the car is less then 100% charged"

There are some still questioning this because basically nobody else has figured this out and other EV's release the regen under these conditions as to not hare the batteries by overcharging. Yes, I know the battery is not "fully charged" when the SOC say's 100% but you can still harm the cells by charging them at such a high rate (the i3 regen can supply a blast of up to 50kW!) when they are nearly fully charged.

By the way, to be specific, the i3 has a 21.6kWh battery (not 22kWh) and the usable capacity is 18.8kWh, so it uses 87% of the full capacity.

 

[Brandon]

my smart ED has regen paddles... 3 levels of regen



Level 1: No Regen, Coasting
Level 2: Standard Regen, Low
Level 3: Max Regen, Strong



its great to just be able to switch between levels whenever, all EV's should have this ability.

 

[Stevei3]

"No, it will still feel the same with the regen as strong as it is when the car is less then 100% charged".

Ha Tom, nice one

electric trains (used to) have braking resistors for rheostatic braking if the electric systems of the railroad did not allow the use of regenerative electric braking. (Many a train in NL had 'em).
My guess: this ancient tech is not built into the i3. These resistors tend to be quite large and heat up very fast. One could imagine one could use the cars heater as a breaking resistor, but this is only 5.5 kW...

BMW can have developed a clever system to use the motor as a brake (for instance DC injection braking or whatever, just Google). This would be very cool engineering wise and would prove that German enginieers just do not quit before everything is done....
Or, just my other guess, the BMW folks present in LA did not grasp the gist behind the original question: where does the energy go ?

Steven

 

[TomMoloughney]

"No, it will still feel the same with the regen as strong as it is when the car is less then 100% charged".

Ha Tom, nice one

electric trains (used to) have braking resistors for rheostatic braking if the electric systems of the railroad did not allow the use of regenerative electric braking. (Many a train in NL had 'em).
My guess: this ancient tech is not built into the i3. These resistors tend to be quite large and heat up very fast. One could imagine one could use the cars heater as a breaking resistor, but this is only 5.5 kW...

BMW can have developed a clever system to use the motor as a brake (for instance DC injection braking or whatever, just Google). This would be very cool engineering wise and would prove that German enginieers just do not quit before everything is done....
Or, just my other guess, the BMW folks present in LA did not grasp the gist behind the original question: where does the energy go ?

Steven

There is that possibility that they didn't quite know what we were asking, but I'm leaning towards they did know. I recently spoke to someone else about this and they said BMW developed a system that activates the friction brakes to simulate regenerative braking in these instances. I'll get more info on this on December 11th when I'll have access to the program managers and engineers.

 

[Stevei3]

...and they said BMW developed a system that activates the friction brakes to simulate regenerative braking in these instances

Hi Tom,

I was always tought to use the engine braking effect going downhill. Using the friction brakes will (obviously ) cause severe wear of and heat buildup in the brakesystem (discs, drums, pads & fluids) which can lead to brake failure @ the bottom. Although NL is very flat, I expect to drive to (and over) the Alps at least once, just to prove to ourselfs that it is possible (with a little planning) should one *really* want.
I am looking forward to any info you are able to acquire !

Thanks & greetings from NL (99% flat),
Steven