All,
I have a RWD model 3 and have I believe experienced the limited regen with winter tires. Rather than going by gut feel I decided to get some empirical data. I've hosted it in a google spreadsheet. I recorded a video of my car with winter tires decelerating from ~45mph to ~12mph and went frame by frame to create a graph. Then I took two youtube videos
https://www.youtube.com/watch?v=F4TpAZZvO1Y &
https://www.youtube.com/watch?v=t8dw4g95eWQ and did the same thing.
Note: These were three different cars running potentially three different software versions, if I get the motiviation this weekend I may swap tires to get a more apples to apples comparison, maybe Tesla will fix it before then.
In the meantime if anyone would like to link me to a video of their speedometer in a car with full regen capability(warm battery) I can add it to the sheet to compare(either summer or winter tires, AWD or RWD).
Anyways the takeaway is with summer tires see about 60% more regen in the 20-40mph range, and regen about equal in the <20mph range
Comparing 30mph as a datapoint
Canuck (winter) = -1.15 m/s^2
My car (winter) = -1.00 m/s^2
Nick's (summer) = -1.92 m/s^2
View attachment 352864
Here is the google spreadsheet link if you want to take a look
Tesla Regen Research
This correlates with some test results I posted a few days ago:
Who has lost regen with winter tires?
I've also noticed something interesting tonight with our fresh snowfall:
The regen below ~ 30 km/h is essentially zero when you are on a snowy side street. To me this really adds credence to the issue that the 'regen issue' people are reporting here is indeed due to the Tesla traction control feedback limiting the regen...likely because they feel it is safer to operate this way and not have the car 'spin out' because someone isn't used to driving an EV where you really should gently remove your foot from the accelerator. Its second nature to me now, but every non EV driver I've let drive my model 3 cant get their head around 'feathering' the accelerator and they end up driving like a 16 year old learning to drive stick
Anyway, I didn't have much time to do a good test but I did capture some accelerometer data showing that the regen below 30 km/h is basically gone when your tires start to 'slip' on the snow. I didn't take a video, but along with this data you can see that the green regen bar 'flutters' a bit, and is essentially non-existent in this instance.
Also, to re-iterate I have an AWD and this regen issue is definitely present. People in the last few pages still seem to keep thinking this is a RWD only phenomenon. Look at my post linked above, before/after winter tires and its 50% less regen at higher speeds, and 'normal regen' at low speeds...until tonight when low speeds also dont work due to the low traction in the snow.
You can see in the plot above the regen force gets to around 0.15g, which is about 1/2 of what it should get to below 30 km/h (should get to around 0.25g from my previous tests)...but then after a second or two the car senses the slipping and lets off the regen and the force dropped off to about 5x less than 'normal' regen and measured around 0.05g.
Oh, and before someone suggests that what I measured above was the car slipping on the snow and nothing to do with the regen, do note that initially the car did slow down fairly quickly, so the tires were gripping the ground. It was the traction control kicking in that caused the force to lessen, not grip on the ground. If I used brakes I still had plenty of grip with the car on the section of road I tested on.
Just to drive that last point home, here is another data set where I took my foot off the accelerator (blue arrow), and after the regen dropped to zero I used the brakes to see if the tires were slipping or not (that the 3 dips indicated by red arrows after the initial regen induced one). You can see quite clearly I was able to use brakes to stop the car. The first two times I tapped the brakes I let up a bit to see if regen would hold at that force and it didn't, then I hit the brakes a bit harder and you can see I was able to grip quite well. Then I hit the accelerator a bit to confirm I could grip the ground.
Again, this leads me to conclude the issue is that the traction control feedback is too sensitive for this use case. There may be other reasons why Tesla doesn't want to change it, but as I've said before: my wifes bolt and my 2 previous volts never did anything like this with regen and winter tires, and I never had any stability issues driving in the winter with those cars.