brake regeneration in slippery snowy roads and traction control

I had a scary ride home last winter on a Vermont interstate in a snow storm. Everyone was going 25 to 40 mph and as I descended a hill on a curve I took my foot off the accelerator and as the brake regeneration came on I began to skid. This was from a speed of 25 to 30. Is there a setting to turn off regenerative braking under these conditions? Should I have been driving with traction control on?

I think it may depend on year of manufacture. On post-LCI models, the recommendation is to use DTC mode - it is designed for those conditions. It can be selected from within the iDrive user interface. It is described in the Owner's Manual.

johnjackgallag said:

I had a scary ride home last winter on a Vermont interstate in a snow storm. Everyone was going 25 to 40 mph and as I descended a hill on a curve I took my foot off the accelerator and as the brake regeneration came on I began to skid. This was from a speed of 25 to 30. Is there a setting to turn off regenerative braking under these conditions? Should I have been driving with traction control on?

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What would happen if one's foot lifted up on the power pedal so that there's no propulsive or regenerative power (i.e., the power gauge at the 6 o'clock position) while lightly pressing the brake pedal with one's left foot to apply friction brakes on all 4 wheels? Pressing the brake pedal results in regen braking as well, so I don't know whether braking could be balanced between front and rear.

I drove on a patch of black ice, as I thought it could be here in this curve near a pond, so I was careful.
But I came across an other bimmer in 5 serie who was too quick and very surprised...
So I release the accelerator, bad idea, the rear wiggled probably due to the regenerative braking only at rear wheels.
Hopefully it stops when I applied a small braking, with the 4 wheels, we passed each other without problems.

I don't have winter or all seasons tire, it's not really necessary where I lived, and with my other gasoline cars (316i and z3) I never encountered this problem.

johnjackgallag said:

I took my foot off the accelerator and as the brake regeneration came on I began to skid.

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When this happens to me, which it does several times every winter because of where I live, my left foot instinctively searches for the clutch pedal. In a situation like this you want to disengage all wheels completely to have what little grip there is for steering and getting the car back on track, and then brake gently to get the speed down without starting to skid again. In the absence of a clutch, here is what I do instead: When I feel the wheels losing their grip, or preferably just before that happens, I shift to neutral. When I suspect or can see that the road is very slippery (covered in ice, with rain or meltwater on it), I keep my right hand on the selector switch to be prepared. Note that to shift to neutral (only ONE click downwards!) it's not enough with a brief click, you have to keep the switch in that position for a few tenths of a second.
When I have regained control, and perhaps braked lightly to reduce speed somewhat, I can continue driving, without stopping, by pushing the accelerator pedal down to where I think it should be given the present speed (nothing happens when pressing the pedal in neutral, at least I've never heard or felt anything), and then shift to drive. I don't need to be very exact with the accelerator position, the car seems to be very forgiving regarding that, and the transition from neutral to drive is completely seamless without any sounds or jerks or anything.
I am a bit concerned though, that this procedure could be detrimental in some way, does anyone have any thoughts or input on that matter?

I remember reading somewhere on this forum that you would have to bring the car to a full stop, and push the brakes to be able to shift from neutral to drive, but that's not the case with my car, a 2020. Perhaps it depends on the manufacturing year?

Another thing I worry a bit about is that I might by mistake move the selector two clicks, and thus go directly from drive to reverse. I don't know if the car would allow that at relatively high speed, and I don't want to test it!
I do know, however, that this is possible at very low speed, like when turning the car around on a narrow road, and you have to go forth and back a few times.

I haven't tested traction control for avoiding problems with braking regen on slippery road, only for when I got stuck in the snow (and it took surprisingly little snow to do that, only like 5 cm/2 inches. Really wet snow though, which is much worse than dry snow). For that situation the traction control was useless, as it kept the wheels turning (slowly) at standstill, even after you had let go of the accelerator, and you had to stop the wheels from turning by hitting the brakes. Spinning your wheels when you're stuck in snow is a big no-no, unless you plan to spend a lot of time on that exact spot.

The weather forecast predicts that temperature will rise to above 0° C/32° F by quite a few degrees in a about a week, so since our village road is completely covered in ice I will probably get a chance to test traction control while on the move then. Will post results here.

Remember since that when you're doing "gear" shifts on the steering column that there are never any gears changing. You are simply providing input as to which direction the energy should be turning the traction motor. That's why there's no clunks or anything like that when shifting it. I have found that if I'm moving forward in D and switch it to R it will do it without me touching the brakes but if I'm moving over roughly 4-5 mph it won't do it so it seems to want me to be going quite slow, which makes sense. 2 weeks ago we got our first snow since I've had the i3S and I never experienced this issue when slowing down in snow but your idea of moving to N makes sense. In my other car I also jump to press in the clutch when there is slippage occurring. In the i3 if you just let up on the accelerator a bit (when slipping while trying to go faster) or press it a bit (if slipping while slowing down) it will also let the car coast. As long as the energy meter in the instrument cluster is in the middle you're essentially in neutral as no power is going to or from the motor.

mojo said:

I think it may depend on year of manufacture. On post-LCI models, the recommendation is to use DTC mode - it is designed for those conditions. It can be selected from within the iDrive user interface. It is described in the Owner's Manual.

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Hiya, this is an interest for me too, as I've already had experience of being unable to go up a hill with packed snow without rear wheel skid, however gently I use the pedals.
What is DTC mode, and would it be available on a 2017 model car (from 2016)?

If your car has DTC mode, it will be described in the Owner's Manual, and in the BMW Driver's Guide app.

As far as I can tell, DTC mode was introduced as part of the LCI "refresh".

mojo said:

If your car has DTC mode, it will be described in the Owner's Manual, and in the BMW Driver's Guide app.

As far as I can tell, DTC mode was introduced as part of the LCI "refresh".

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DTC is a subset of the more advanced DSC. So we have it.

TRACTION mode turns off the advanced DSC mode and reverts to DTC. So allows power to the wheels even when it slips. Thus getting out of slippery conditions even when one wheel spins as DSC would chop the throttle to prevent a high speed skid. There are whole sections in the manual explaining Dynamic Stability Control which in the event of a high speed skid - brakes the inside wheel to bring the car straight - then will also apply an opposite steer into the skid as well. It’s clever. But too clever when you are stationary on ice or snow. Hence selecting TRACTION warns you that you are turning ‘off’ DSC. Thing is that is colloquially known as ‘traction control’ and no one in their right minds would ever turn that off as they might die. However they would stay stuck as many rear wheel drive BMW seem to do every winter since they removed the ‘snow’ button.

Screen shot

2 more shots showing we do have DTC. As far as I know it existed from day one.

This winter, lowered the PSI on the snow tires to 25 in the front and 29 in the back, and turned “on” the “traction” feature. The difference has been amazing. Still slips when trying to find traction from a complete stop and still need to take it easy on corners when icy. But overall, no issues or concerns like I did last year when the tires were fully inflated. So much so, I haven’t notice much issue with regen braking causing me problems this winter.

Gonville said:

2 more shots showing we do have DTC. As far as I know it existed from day one.

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What year is the car that the photos were taken from?

My reply reflects what BMW says in its documentation on what was changed as part of the LCI "refresh":

New Traction Control

DTC is turned on and off using the iDrive controller. The BMW i3 had previously also had Dynamic Traction Control. But this was limited
only to the lower speed range up to 30 mph and essentially designed for straight-ahead driving.

The DTC function was also modified when the new cruise control function was introduced in the BMW i3s for 11/2017. This means that maximum traction is available in the speed range over 60 mph and more drive power is permitted even when cornering.

Special Automatic Stability Control has been developed for the demands of a highly dynamic electric drive. The control cycle works noticeably quicker than the previous ASC system. The ASC system also operates during recuperative deceleration of the vehicle and ensues that the deceleration can be maintained, even given difficult road surface conditions (rain/snow), and hence more energy can be recuperated. This results in improved stability, traction and availability of energy recovery in all driving and ambient conditions. In addition, an expanded and redesigned DTC mode ensures enhanced traction, particularly on loose surfaces and even more driving pleasure over the full speed range.

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The problem with that document is that it mixes things up, so it's never completely clear whether it's referring to a feature of the LCI model or just an i3 in general! But it seems that the way that traction control operates is definitely different on the LCI models.

kd7iwp said:

Remember since that when you're doing "gear" shifts on the steering column that there are never any gears changing. You are simply providing input as to which direction the energy should be turning the traction motor. That's why there's no clunks or anything like that when shifting it.

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Thanks for your answer. I suspected that drive/reverse was done by altering phase sequence to the motor, but since I'm not familiar with this type of electrical machine (hybrid something, I seem to recall), I wasn't really sure that it wasn't done by gears. I did believe though, that Neutral meant that the wheels and driveshafts were mechanically disengaged from the motor, but maybe they are permanently connected and Neutral is realised by letting the motor spin with the wheels without neither inserting nor extracting current? Please let me know if I'm correct in this assumption. In that case I don't think I need to worry about any damage coming from shifting between Drive and Neutral while on the move.

kd7iwp said:

I have found that if I'm moving forward in D and switch it to R it will do it without me touching the brakes but if I'm moving over roughly 4-5 mph it won't do it

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OK, so then I don't have to worry about pushing the gear selector lever too far either.

Thanks!

I drove in 6" deep snow , packed snow and ice in January (UK,N Staffordshire about 150m above sealevel)
Eco pro mode, very delicate throttle use, released pedal gently to avoid regen kicking in. No real issues . Managed to get up a small drive with hard packed snow at 2mph, barely moving, Traction Control (2016 94AH) kicking in occasionally.
Ditto muddy roads..
I take care not to park facing up or down hills in ice and snow.. startup can be very difficult
Standard tyres: my Honda Jazz with Michelin Cross Climate had better grip but less control at low speeds even with it being an auto.. less smooth throttle response. I drive as if I am caressing an egg with my throttle foot.

Gonville said:

DTC is a subset of the more advanced DSC. So we have it.

TRACTION mode turns off the advanced DSC mode and reverts to DTC. So allows power to the wheels even when it slips. Thus getting out of slippery conditions even when one wheel spins as DSC would chop the throttle to prevent a high speed skid. There are whole sections in the manual explaining Dynamic Stability Control which in the event of a high speed skid - brakes the inside wheel to bring the car straight - then will also apply an opposite steer into the skid as well. It’s clever. But too clever when you are stationary on ice or snow. Hence selecting TRACTION warns you that you are turning ‘off’ DSC. Thing is that is colloquially known as ‘traction control’ and no one in their right minds would ever turn that off as they might die. However they would stay stuck as many rear wheel drive BMW seem to do every winter since they removed the ‘snow’ button.

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This is good to know - thanks for the information. Where I live we get relatively little snow or ice, but since I am near the ocean I often encounter loose sand. On a couple of occaisions I have been concerned about getting moving again when parked on a sandy area.

tordon said:

I did believe though, that Neutral meant that the wheels and driveshafts were mechanically disengaged from the motor, but maybe they are permanently connected and Neutral is realised by letting the motor spin with the wheels without neither inserting nor extracting current?

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It's the latter. The motor is permanently connected to the drive wheels via a gear reduction unit, a differential, and axle half-shafts. No gears ever "shift" or disengage in the i3's very simple drivetrain.

alohart said:

It's the latter. The motor is permanently connected to the drive wheels via a gear reduction unit, a differential, and axle half-shafts. No gears ever "shift" or disengage in the i3's very simple drivetrain.

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Thanks for that, Alohart. Another important piece of the i3 puzzle.

mojo said:

What year is the car that the photos were taken from?

My reply reflects what BMW says in its documentation on what was changed as part of the LCI "refresh":





The problem with that document is that it mixes things up, so it's never completely clear whether it's referring to a feature of the LCI model or just an i3 in general! But it seems that the way that traction control operates is definitely different on the LCI models.

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The first photo is from my 60Ah 2014. Used many times on UK forum. Idrive 4 I think? The next 2 are idrive 5 as seen from the image of the car which isn’t on the lower res pre LCI. I updated the pictures when I received the 2017 94Ah. So yes we had it back then for the first 3 years.