Regen and creep operation?!

[jadnashuanh]

Since June 2014, mine gets activated multiple times per trip...so far, so good. On my GT, with the auto hold enabled (I wish the i3 had this), it does exactly the same thing on its own once you come to a full stop. That one was bought in April 2011 and still going strong. Seems like it works just fine to me. Now, it could stop tomorrow, and I might be pissed, but so far, so good. I find it more relaxing to not have to be pressing the brake pedal when stopped for awhile.

 

[eNate]

Oh yeah! Now that you mention that, in addition to the mechanical parking brake on my Audi that would auto-release when I stepped on the gas, it also had the Hill Hold Assist feature that would automatically hold the brakes when stopped on an incline. Hill Hold Assist did not use the mechanical parking brake, so must have been integrated into the hydraulic system. No brake system trouble over 100,000 miles.

And then there was my Subaru wagons with a manual transmissions. They had something similar, and my recollection is theirs used a rudimentary ball or plunger that was displaced by gravity on a slight incline (only when the clutch was depressed) and slid to block the brake line, holding pressure. Those systems were 100% reliable over the miles I owned the cars (150,000 and 180,000).

 

[frictioncircle]

I can't recall ever being stopped behind an i3 at night at a dark intersection. Are our brake lights particularly bright?

Out here the i3 is popular – being stopped behind one at a traffic light is a frequent experience so I've researched this quite a bit.

I don't think our brake lights are excessively bright. I've certainly seen brighter on some of the newest BMWs, brighter to the point of being painful. One thing I've not seen is an i3 with the lower brake lights illuminated. Maybe a panic stop is what it takes to get them going?

However, our rear turn signals are quite bright. I'm ok with that as I like folks to be aware that I'm turning or changing lanes. Some recent cars (VW Touaregs and Jettas in particular) have rear turn signals that are so well integrated into the brake lamps, it's easy to miss them. The fact that they're red doesn't help either!

 

[alohart]

One thing I've not seen is an i3 with the lower brake lights illuminated. Maybe a panic stop is what it takes to get them going?

Also, driving with the hatch open will cause the lower brake lights to illuminate when braking.

 

[eNate]

Follow-up question:

What is the anti-rollback mechanism on the i3? It certainly isn't the parking brake.

Does it hydraulically engage the brake if it senses rearward movement?

Does it engage a one-way clutch somewhere along the drivetrain?

Is it electrical resistance being applied through the motor?

Whatever it is, it doesn't seem to prevent the forward creep that's the topic of this thread. Or does it only engage in situations where it senses rollback is possible (stopped on a slope)?

 

[alohart]

What is the anti-rollback mechanism on the i3? It certainly isn't the parking brake.

Is it electrical resistance being applied through the motor?

When stopped on a steep hill, I have seen the power gauge move up which makes me think that power is being applied to the motor to prevent the car from rolling.

Whatever it is, it doesn't seem to prevent the forward creep that's the topic of this thread. Or does it only engage in situations where it senses rollback is possible (stopped on a slope)?

If an i3 is in D, power applied to the motor couldn't prevent it from rolling forward. Likewise, if an i3 is in R, power applied to the motor couldn't prevent it from rolling backward.

I think this is additional evidence that anti-rolling is implemented by applying power to the motor.

 

[3pete]

I think this is additional evidence that anti-rolling is implemented by applying power to the motor.

I have no technical expertise on the subject but this seems plausible.

One other thing I've noticed is: if you are stopped and holding still due to the 'anti-roll', and put your foot on the brake, something happens that you can slightly feel in the brake pedal. Then, if you take your foot off the brake, you'll roll back ever so slightly before the anti-roll stops you (like, an inch or less). If you keep repeating this, it keeps happening which makes me think there's a hand-off between anti-roll and actual brake. Initially I thought it was the car activating the parking brake, but it sounds different than that and I could see where energizing the motor would have a similar effect.

I also feel like I have been on steep enough hills where the anti-roll did NOT hold the car immediately, but I didn't do much testing because I quickly hit the brakes since a) I wanted to be stopped, not rolling backwards at all and b) it seemed going backwards in Drive would be bad.

 

[tjsean0308]

Funnily Tesla introduced "Creep' for the Model S to accommodate USA drivers who were used to automatics - sad but true. And our absolute favourite EV feature is regen so going back to having to brake (like a primitive ICE car) in traffic is a bummer. Indeed I'd like far stronger regen - I read that the 64Ahr i3's had stronger regen and new-to-EV drivers found it made driving jerky so they moved a bit of the regen across to the brake pedal in the 94Ahr model. Can anyone confirm if this is true - certainly the demo 64Ahr i3 we test drove seemed to have more regen.....

94Ah driver here. The last diode of the regen indicator does not light until you just barely press the brake pedal. Just the throttle pedal will bring the car to a stop, but it's not the full regen the car is capable of. I'm not sure at what point the ABS also slows the car with the friction brakes, but just hovering on the brake pedal lights up that last diode and really throws out the anchor.

 

[robthebold]

Follow-up question:

What is the anti-rollback mechanism on the i3? It certainly isn't the parking brake.

Does it hydraulically engage the brake if it senses rearward movement?

Does it engage a one-way clutch somewhere along the drivetrain?

Is it electrical resistance being applied through the motor?

Whatever it is, it doesn't seem to prevent the forward creep that's the topic of this thread. Or does it only engage in situations where it senses rollback is possible (stopped on a slope)?

It uses the motor to hold the car. I found it in the manual, I think under efficiency techniques -- it said that anti-rollback uses a small amount of electrical power. So I learned this indirectly and purely by accident -- I was reading the on-screen user manual to alleviate boredom while waiting in the school pickup line. (And unlike everyone else, I observed the "no idle" signs!)