Regenerative breaking stuck on low after the last SW update

[Ande]

Anyone want to try opening their mind to a different perspective? It's possible the change was for battery health and reduction in degradation over time..

NO. it simply does not make any sense. At best, this fuc*Op hurts the battery.

When I preheat the car for whatever period, it does NOT power the coolant heater, not at all, regardless whatever it is connected to the power grid or not. Once I start to drive, the coolant heater is working at 100% until the battery reaches some decent temperature.

So: This bug is actually spending more of the battery, increasing the chemical cycles the battery need to work (aka: aging it faster), rather than if it was preheating from the mains.

This is a shameful bug, the shame lies in tesla being so impressively ineffective at correcting it, it took now >6 months of inconvenience here in Norway, hundreds or reports, and Tesla does NOTHING. Except... they sabotaged AP by increasing nagging at the whims of the european car indrustry + corrupt EU. That they did almost over-night.

I always loved Tesla, now that they clearly retroactively implement nasty regulations, abusing the upgrade option, and prove that they do not care about new bugs .. it is not so easy anymore.

 

[Battpower]

Once I start to drive, the coolant heater is working at 100%

What battery temperature at start? How do you know battery heater is on at 100%? What power is the heater?

How long does heater stay on? I have tried to think of a good algorithm for this reheating, but I think it must be a user choice. Unless the car knows for sure what the next journey requirement will be, I don't see how the car system can know if preheating will make sense.

Personally, I would have thought that the load of preheating would show clearly in very poor watt hrs per mile.

 

[Ande]

What battery temperature at start? How do you know battery heater is on at 100%? What power is the heater?

How long does heater stay on? I have tried to think of a good algorithm for this reheating, but I think it must be a user choice. Unless the car knows for sure what the next journey requirement will be, I don't see how the car system can know if preheating will make sense.

Personally, I would have thought that the load of preheating would show clearly in very poor watt hrs per mile.

I sniff the BMS.
I did not yet care to log fully what temperature it stops at , or what is needed to have a decent/full regen , but I may do so (usually, I do not reach the target temp during my 30-min trips)
The MAX-Charge in regen is set to 0kw already at +3°C or so, The heater is 6KW (working of high voltage)

I may plot the temperature vs heater vs max-charge tomorrow, will drive for an hour or so.

 

[Battpower]

I sniff the BMS.
I did not yet care to log fully what temperature it stops at , or what is needed to have a decent/full regen , but I may do so (usually, I do not reach the target temp during my 30-min trips)
The MAX-Charge in regen is set to 0kw already at +3°C or so, The heater is 6KW (working of high voltage)

I may plot the temperature vs heater vs max-charge tomorrow, will drive for an hour or so.

Yes, I understood heater power something like 6 or 7 kW, which of course is needed to make a useful contribution to raising heat of large battery mass.

From casual observation and comparison with other EV, I expect driving Model S at 100 kph on good level surface with optimal weather maybe requires 10 to 15 kW, so heating battery for even 15 minutes could be equivalent to driving may be 15 km.

So running a 6 kW battery heater load is a big waste in many cases I think, and could easily be 50% of average total power in some cases. Drive 20 minutes to work. Park car all day which of course goes cold. In reality you will likely use far more energy than you will save, and for those who 'like the feel of regen braking' - and I am one of those - is it worth reducing your cars efficiency by 20% or more on short runs just so you get regen?

If you are able to get some accurate data, that would be really interesting, especially to help understand where the crossover temperatures, limits and extremes are. Just to see if my gut feeling is anywhere near, I think 10 to 13 or 15 deg C battery core temp takes you from 30% to 90% regen.

In fact, maybe there is only one situation where battery heating makes sense and that is to warm a cold battery before fast charging. Frees up charging stalls quicker, less strain on battery, allows higher charge rates. And, once you have kick started higher charge rate, the battery self heats so you can soon shut off the heater.

 

[Ande]

Weather: -2°C
SoC at start 78% , not last charging was many hours before driving.
Driving time 1 hr , only 60-90km/h (on snow/ice)

The way "Scan My tesla" logs to CSV is an absolute mess, so it took some time to produce these numbers without programming.

In short: Heating is switched off somewhere near 22KW charging limit.
The BMS-MAX-Charge is not perfectly proportional to cell average, maybe some other temperature.
It takes some good 18 minutes before decent regen. (longer in colder conditions, or with colder battery at start)
The regen in main display is fake, when regen reaches 30kW , the main display does no longer show any regen limit.

 

[one-ten]

Yes, the display is fake, today it was 7 degrees celcius, and the line was at about 10 regen, but actually you don't have any regen then...