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Premature 'preconditioning battery for fast supercharging...?'

holmgang

Active Member
Sep 9, 2019
1,389
1,534
eu
Anybody seeing super premature preconditioning?

Typically precondition happens before 10/5 minutes of arrival of Supercharger. Recently I've seen it start to precondition -- on and off! -- at around 60 minutes / 60km away from Superchargers.

All occurences were with battery already warmed (power bar shows no dots); car had already been driven for 1+ hours; and ambient temperature was mild. Basically, no reason that could be seen for the car initiating the precondition. It would start it at 60 minutes before arrival, maybe stop at 50, start again at 30, stop at 25, etc.... seems completely unecessary.

No cause for real alarm but I found behavior strange.
 
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Anybody seeing super premature preconditioning?

Typically precondition happens before 10/5 minutes of arrival of Supercharger. Recently I've seen it start to precondition -- on and off! -- at around 60 minutes / 60km away from Superchargers.

All occurences were with battery already warmed (power bar shows no dots); car had already been driven for 1+ hours; and ambient temperature was mild. Basically, no reason that could be seen for the car initiating the precondition. It would start it at 60 minutes before arrival, maybe stop at 50, start again at 30, stop at 25, etc.... seems completely unecessary.

No cause for real alarm but I found behavior strange.
it takes time ! Today outside temps was 1c , preconditionning started 50min before arrival at 25c battery tempeature, arrival temp was 35c and during chaging battery heated upto 55c !

When battery is below 20c supercharging is limited to 30kw which is really slow
 
That's it... The regen will not show any dots once the battery reaches around 11C (52F). Good supercharger performance requires at least 40C (104F). Since heating the battery is slow, it starts early. Recent software updates changed the temperature at which you have full regen, the bettery needed to reach 20C (70F) before. They might also have enhanced the logic that decides when to start preconditioning so that more people get full SC speed. If you have a single motor it's even slower to heat. 1h in advance doesn't look that long to me from what I've seen using scanmytesla on my dual motor.
 

Gasaraki

Active Member
Oct 21, 2019
2,338
1,665
Syracuse, NY
Anybody seeing super premature preconditioning?

Typically precondition happens before 10/5 minutes of arrival of Supercharger. Recently I've seen it start to precondition -- on and off! -- at around 60 minutes / 60km away from Superchargers.

All occurences were with battery already warmed (power bar shows no dots); car had already been driven for 1+ hours; and ambient temperature was mild. Basically, no reason that could be seen for the car initiating the precondition. It would start it at 60 minutes before arrival, maybe stop at 50, start again at 30, stop at 25, etc.... seems completely unecessary.

No cause for real alarm but I found behavior strange.
That's totally not true. 5-10 mins is not enough time to precondition the battery especially if the outside temperature is cold. It will start the preconditioning of the battery when it thinks it will take that long to precondition the battery. Stop second guessing the car.
 
So I noticed this the other day as well... I was driving to a supercharger that was 111 miles away. The outside temp was 50F, and as soon as I began my trip I noticed that it was preconditioning, something it has never done so early for this particular supercharger. I thought it was odd to precondition about two hours ahead of time, so I just turned off navigation to the SC and then turned it back on about 15 minutes before arrival.
 
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I think this is part of the "optimizations for cold weather" that were in the release notes of the recent software updates. If you have a single motor (SR+), it's very difficult to generate heat from it while moving the car forward. It will take a huge amount of time to heat the battery while driving, which would explain why it starts earlier now. I've seen many people in Quebec complain that they get poor charging speed at superchargers in winter even when preconditioning. I think the previous algorithm was arriving with a cold-ish battery. A dual motor has the luxury of a front motor that is normally not used to propel the car so it can get ~3kW of power to generate heat.
You can disable it, and risk having slow supercharging speed. It's your choice.

EDIT: I see your sig listing a Stealth, which means you probably have two motors. Even then, the battery needs to be at least 100F for reasonable charging speed. If it's 50F outside, that will take a huge amount of time to heat...
 
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I think this is part of the "optimizations for cold weather" that were in the release notes of the recent software updates. If you have a single motor (SR+), it's very difficult to generate heat from it while moving the car forward. It will take a huge amount of time to heat the battery while driving, which would explain why it starts earlier now. I've seen many people in Quebec complain that they get poor charging speed at superchargers in winter even when preconditioning. I think the previous algorithm was arriving with a cold-ish battery. A dual motor has the luxury of a front motor that is normally not used to propel the car so it can get ~3kW of power to generate heat.
You can disable it, and risk having slow supercharging speed. It's your choice.

EDIT: I see your sig listing a Stealth, which means you probably have two motors. Even then, the battery needs to be at least 100F for reasonable charging speed. If it's 50F outside, that will take a huge amount of time to heat...
Makes sense. It's supposed to hit 84F this weekend, so I'll leave the car parked outside for the day and then give it another shot. Not a huge deal either way, just a different behavior than I'm used to!
 
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I just experienced this on a recent trip. I get it may need to start early. But mine started over a hour out, stopped and started about 4 times. So it sucked more power starting and stopping. Why not just do it once ?
Starting and stopping doesn't suck more power. It's just starts spinning or not. Need to stop thinking like ICE cars or florescent bulbs.
 
I have not monitored the battery preconditioning via SMT recently but when I did battery temp reached around 100F prior to arrival at the Supercharger. At that time my RWD would start warming the battery around 30 to 40 minutes out. With similar temps it now starts 90+ minutes out. If the heating is starting and stopping during that 90 minute period, looks like the algorithm used to determine when warming should start was better before? BTW, my buddy who owns a Dual motor M3 sees the warming starting much earlier now. He pressed on the screen preconditioning message and the message went away but the battery heating did NOT stop (he was monitoring via SMT).
 
That’s fine. Still does not explain why it starts and stops pre-condition. It used to just run it 30-40 minutes before you arrived at the supercharger.
OK, let's say you are driving at 65mph on the highway and the temperature was 60F and the battery was a 25C. The car "guessimates" that it should start preheating 45 mins before in order to get the battery to 40C at the Supercharger.

Now suddenly the temperature rises or you drive faster or you're going uphill or downhill or whatever. How is the car supposed to know that? If your heat generation increased suddenly then it would stop the preheating. Then if it thinks it needs it, then it will start it.
 
Based on what just happened, it seems buggy. Just started a trip, battery at 95% and planning to stop at a supercharger 1:30 away and the pre-conditioning came on. Outside temperature was 50 deg F. I submitted this as a bug report, because this just can't be right!
I drove from DC to Illinois the other week. I drove from DC to Breezewood, PA. Stopped for probably 30 minutes tops to charge and then drove from another 2 hours+ to the next super charger and still it required me to pre condition for 40 minutes. It seems to take a lot to pre condition when it's 50F or below outside no matter if your battery is cold or not.
 
I drove today and looked at preheating with scanmytesla. A while ago, it would heat the motors to 90-100C and use that to warm the battery. Now instead it heats them just a few degrees higher than the battery and circulates that a bit. Once it needs more heat, it starts warming the engines a few more degrees. It's more gentle on everything and srresses the motors much less in heat.
I believe it's not using significangly more power and probably creates less stress.
 

Gasaraki

Active Member
Oct 21, 2019
2,338
1,665
Syracuse, NY
I drove today and looked at preheating with scanmytesla. A while ago, it would heat the motors to 90-100C and use that to warm the battery. Now instead it heats them just a few degrees higher than the battery and circulates that a bit. Once it needs more heat, it starts warming the engines a few more degrees. It's more gentle on everything and srresses the motors much less in heat.
I believe it's not using significangly more power and probably creates less stress.
Right. We have backyard engineers that "believe" or "think" that "it can't be right" without really knowing what's happening in the background. :rolleyes:

That's why companies hide information from us. You put a notification on the screen, people complain "it's too early, it's too late", etc, etc. They should just do it and not tell people. Like Apple says, people don't know what they want. Less choice is better.
 
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Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
6,868
13,496
Springfield, VA
I just experienced this on a recent trip. I get it may need to start early. But mine started over a hour out, stopped and started about 4 times. So it sucked more power starting and stopping. Why not just do it once ?

It preconditions longer so that the batteries warm completely to the center of the cells. Starting and stopping allows the battery pack to come up to temperature gradually and evenly. This results in better charging performance and likely better battery longevity.
 
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