Regen and creep operation?!

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GuyD

Active member
Joined
Jun 6, 2018
Messages
32
We have now had our i3 for well over a year and are generally very happy with it - it is now our 'go-to' car and the ICE cars languish in the garage. Charged from solar so we notice the savings!

The steering is much improved since we had the tracking/alignment done by BMW (rather than a tyre fitment place!)

I've recently noticed odd behaviour and curious whether others have had this experience. Sometimes when driving in traffic fairly slowly the regen seems to stop working (ie the car coasts rather than slowing) - this is not with a full battery. Catches me out as I've become so attuned to the regen.
The car sometimes creeps on zero throttle (and thumps when drive/reverse is engaged) so it seems that a bit of residual motor action is occurring on no throttle. BMW did reload the motor control software at the last service but this doesn't seem to have cured the quirk.

Any ideas/suggestions out there?
 
Sometimes when driving in traffic fairly slowly the regen seems to stop working (ie the car coasts rather than slowing) -

Is the road at all rough/bumpy when this happens? The regen braking is designed to disengage to protect the drive components if the car hits a bump, dip, or turns sharply. I have a stop-sign near my house that I hit on an almost daily basis. There is a very slight bump/washboard coming up to it, and as one-pedal regen braking slows the car approaching the stop sign, the regen braking cuts out and the car coasts every time the wheels hit the bump.
 
Thanks Mark for the input.

No it usually happens in traffic on smooth roads! I have noticed that if I lift off and slow on regen on a gravel road and there is any 'irregularity' , the rear wheels momentarily lock up or skid and then the regen licks out.

The fact that it also creeps and thumps into drive seems to indicate some elec supply to the motor with no throttle - this only occurs occasionally
 
I wash a rotors and calipers once a while to keep them dust free and hit brakes hard once a day to clean rust bc if you use only regen they rust bad and make creepy noise at least in my case try maybe you solve your problem brake pads should last “ forever”
 
Wonder if you have a slightly loose/damaged suspension or drive train component, which is giving you the 'clunk' you hear when shifting, and moves just enough out of 'true' on occasion to have the regen braking disengage, but not enough to trigger the dreaded 'drive-train malfunction' error??
 
That is an interesting thought re the loose suspension but I have just had the alignment done so surely they would have picked up a loose/damaged suspension part?

On the other hand since the alignment I have noticed an improvement in the steering but the car seems more sensitive to winds and road camber now....

Puzzling but not a major issue so far.
 
since the alignment I have noticed an improvement in the steering but the car seems more sensitive to winds and road camber now....

Maybe the result of a change in tire pressure? If the tires were low, and they added air during the alignment.
 
I always keep the tires at 2.4bar front and 2.9 bar at the rear as advised by the BMW agent. Tires new at rear, still good at the front.

What is the expected tire life? I got just over 30k km on the rears and then they were done. Fronts on 33k kms and still good - 60-70% wear I'd guess.

Returning to the first query - I suspect somewhere in the motor controller, the motor is giving a couple of percent of power/eletron flow on zero throttle (occasionally) so nullifying regen at slower speeds; causing some creep and making the thump on engaging drive. Not a big issue for now. Just curious to see if it was commonplace.
 
The regen not only changes when it detects slip (that includes hitting a bump), it also is tied into the steering wheel angle, so the tighter the turn, the less regen will be produced. From a performance issue, braking in a turn can upset the balance, especially on a vehicle that is only driven by one axle and only one producing regen (braking). It's a good way to induce a spin if the surface isn't perfect. Think handbrake turns...
 
Just a thought , could there be an issue with the pedal position sensing mechanism and/or electronics ?
 
CanisLupus said:
Just a thought , could there be an issue with the pedal position sensing mechanism and/or electronics ?

Hi, That's exactly what I'm thinking...…

Today the creep came and went (all this is on smooth roads at low speeds and in a straight line!) It is very slight and not an issue as such but it is occasionally disconcerting to have the car not slow on lift-off or creep slowly towards the car in front (on the level!) - especially when I am expecting it to be sitting stationary...…..

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.....
 
CanisLupus said:
Just a thought , could there be an issue with the pedal position sensing mechanism and/or electronics ?

Hi, That's exactly what I'm thinking...…

Today the creep came and went (all this is on smooth roads at low speeds and in a straight line!) It is very slight and not an issue as such but it is occasionally disconcerting to have the car not slow on lift-off or creep slowly towards the car in front (on the level!) - especially when I am expecting it to be sitting stationary...…..

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.....
 
Remember that the 'Hill Hold' function will keep the i3 from rolling backwards when stopped on an uphill (unless the hill is too steep) but when stopped on a down hill of any grade the i3 will indeed creep forward unless the brake is engaged to the friction level .
 
The hold function prevents the car from moving in the opposite direction of the 'gear' selector, so also works in reverse.

In some places in the world, it's considered bad (and rude) practice, to sit at a stop or light with your brake applied. They use their parking brake. If you haven't tried it, on the i3, as long as you've got your seat belt on, the car WILL automatically release the parking brake when you touch the go pedal. If you're one of those that don't wear your belt, you'd have to manually turn the brake off which also requires you to first push on the brake pedal.

I find that very convenient. WHat I miss that's on my other BMW, is a setting called automatic hold. That automatically applies the parking brake once you are fully stopped, and releases it when you hit the gas pedal. No worry about creeping as long as you don't accidentally hit the gas pedal. I'd like it even better if I didn't have to turn it on each time, as it defaults to off.
 
jadnashuanh said:
In some places in the world, it's considered bad (and rude) practice, to sit at a stop or light with your brake applied. They use their parking brake.

I'm curious about this:
Where are these places?
Why do people care what method you use to be "stopped at a red light"? / Why is the brake "rude"?
Why is the parking brake preferred (do these places have a large star-gazing community and dislike the excess light pollution from brake lights of cars stopped at an intersection)?
What if you get rear ended?

#so_many_questions
 
3pete said:
jadnashuanh said:
In some places in the world, it's considered bad (and rude) practice, to sit at a stop or light with your brake applied. They use their parking brake.

I'm curious about this:
Where are these places?
Why do people care what method you use to be "stopped at a red light"? / Why is the brake "rude"?
Why is the parking brake preferred (do these places have a large star-gazing community and dislike the excess light pollution from brake lights of cars stopped at an intersection)?
What if you get rear ended?

#so_many_questions

I've heard this applied to Britain. I don't know how true or widely adopted it's followed, just forum posts.

Some cars put out a blindly bright amount of brake light. So I can see how it might be interpreted as inconsiderate to blind the occupants of the car that stops behind you at a long stoplight, particularly out in an area away from bright city lights. With the automatically disengaging parking brakes that are showing up in many cars, it would be pretty easy to adopt this technique. I don't suppose you would do it if a car wasn't stopped behind you, to address your rear ender concern.

I can't recall ever being stopped behind an i3 at night at a dark intersection. Are our brake lights particularly bright?
 
It was a member from the UK that mentioned the thing about the parking brake at a stop. Especially with the advent of the third, high center brake light long ago now, you can have a pretty bright lamp shining in your eyes. SOme brake lights are higher than others, too, and that can make a difference. Many places outside of the US still are driving a lot of compact cars, so they tend to be lower, and sometimes, a bigger one can really be in your face.

This also probably comes from the manual transmission...using the parking brake is much more common at a stop to ensure you're not going to coast when you release the brake to then get onto the clutch. Those habits tend to carry over. All of my early cars had a manual transmission, so it became a habit for me to use the parking brake at a stop. Over 60-years, I've not had someone fail to notice my car and fail to stop. I've been hit by an idiot that thought he could brake at the last moment on glare ice, but that's a different issue altogether.

I think it also helps to ensure that the emergency brake cable stays free rather than getting gunked up, then sticking if it isn't used regularly.

If you've got some idiot steaming up behind you while stopped at a light and oblivious to your presence, you could always hit the brakes. I've done that a few times, but that also means you have to be paying attention yourself! Most of the time, the running lights are on, so even during the day, there are some lights on back there. The more likely problem is some idiot, during poor traction conditions, is just too close and going too fast and brake lights or not, they'd end up hitting you. If you've got room to move, try to move out of their way without getting broadsided yourself in the process!
 
Ah, that makes sense. The only time I've been blinded by anyone's brake lights was when the plastic was broken off and it was the bare, white bulb shining directly into my eyes.

When driving a manual, I try to make a point of pressing the brake if no one is stopped behind me just as an added indication that I'm stopped there even if it's not required by the incline of the street. If someone's behind me, I'm definitely more likely to take my foot off the brake and just sit on flat ground but I can't remember the last time I used the parking brake to hold at an intersection.

On the other hand, in the i3 I sometimes use the e-brake for the novelty.
 
One thing I'd be curious about is the longevity of the parking brake motor. If the i3 is anything like my last car, there's a small motor on each rear caliper that screws the pads down to a clamped position, and I can hear the motor "wind up" a bit as the torque builds to achieve holding force.

If that gets used with as much greater frequency as this technique entails, is that asking for early trouble?

As an alternative, I'm imagining a system that requires the driver to apply the necessary system pressure at the brake pedal, then closing an in-line solenoid to hold that pressure. But that introduces a new complexity in the brake line that might cause air leaks, fluid leaks, or who know what. So nevermind? :D
 
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