I have installed Scan my Tesla on my M3SR+, one of the reasons was to monitor regen and better understand its behaviour for high speed breaking and mountainous areas on the road. Unfortunately there is only one param on regen and it doesn’t t seem to provide any useful information. BUT I have access to my battery temperature. To get a good stable regen it has to be above 20c which is difficult during winter. Here is a map to battery temps and regen. I will update it later:
>25c full stable regen
>20c good stable regen
>14c and <18c unstable regen above 70km/h
<14c weak stable regen at all speeds
<2c no regen
And again it is VERY difficult to heat up battery from 0c to 20c, it can take 2-3hours. if it is raining, snowing : add more time ! Basically the purpose of all this study is to go further in less time during winter.
Regen amount will also depend on state of charge.
So if I'm reading correct, you're saying that
specifically between 14C and 18C, and above 70km/h, you get weird regen behaviour? Wow. That's oddly specific. By "unstable" do you mean it's cutting in and out like on a slippery surface?
It's very difficult in a model 3 that only has a rear motor because it can only make so much heat. You will also find in the RWD cars if you are blasting down the freeway it can only make so much waste heat because the motor still have to produce forward momentum. From what I've seen with the car trying to preheat the battery it actually produces heat for the battery much faster when the car is either stopped or moving slowly, not when it's going quickly down the freeway. With dual motor, this isn't really an issue because you have twice the heat generation AND even with the rear motor moving the car the front can basically be on full heat duty.
Unless you're preconditioning the battery for Supercharger arrival, the AWD version behaves nearly identically to the RWD in cold conditions. The front motor is almost never used and is just coasting for highway travel - it still can take hours to to warm the battery by 20C, since only the rear motor is really doing work. AWD is also warming a larger battery pack, more thermal mass - it can actually take longer in theory compared to SR+.
Only when the battery is below about 0C (and not en route to a Supercharger) will the front motor be actively making heat. This isn't a super common scenario since the car doesn't allow it to rest significantly colder than that anyways
I've scheduled service for later this week. Interesting to find out if this can be fixed. The biggest oddity in my opinion here is that sometimes when I brake I have to "fight" against the car. In other words, if I don't brake, the car maintains speed or even slightly accelerates. Rather than just slowing down "normally", like all cars to when the foot is lifted from the pedal. This can in no circumstances be considered normal behavior.
Throughout this thread it really sounds like it's somehow accidentally set to cruise, which is really really weird.
There IS a minor bug with turning cruise off that impacts regen (I haven't actually tested this in a while, might be fixed). In these scenarios, are you manually turning off cruise then lifting off the pedal?
It's worth noting that in the Owner's Manual, it's sometimes expected that regen doesn't work for a while after switching to winter tires (and vice versa). It should eventually start working again though.
The other note I'd make is that letting off the accelerator without regen sometimes
feels like acceleration even though it's not. I know by looking at speed and such it's not, but my darn brain absolutely swears it accelerated briefly,
probably because it was expecting deceleration. This still messes me up even though I'm aware of it, it's just a hard-wired weird brain bug.
And a final note - this car coasts like no other. It's has significantly less drivetrain drag than an ICE vehicle, so it can really coast a lot further with a lot less deceleration. The "Low" regen setting is actually sort of similar to ICE vehicle "coasting" (and yet, it's actually recovering energy). This part of the car's behaviour is entirely normal.