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There are some users on the Norwegian EV forum that report that sometimes when they arrive at a supercharger with close to 0%, the car can sit and trickle charge for 10-20 minutes before getting meaningful charging power. One user will always charge on CHAdeMO to over 10% and then switch to supercharging, to avoid this issue...
I really try to avoid going below 10%. It does the battery no good, power is limited, you have no buffer for unexpected detours, you may stop unexpectedly and you may be waiting a long time if you're planning on charging at a supercharger. In my opinion, there are few situations where it's worth the hassle/risk.
But of course, Tesla should do everything possible to ensure that the estimation for remaining available capacity is as good as possible. I think this is the reason why you often can drive below 0 miles. I think the BMS will basically say:"best-case, you can pull 70 kWh from the battery, worst-case around 68 kWh", and then 68 kWh is 0%/0 miles, and you have a 0-2 kWh zero mile buffer. If this estimator screws up by a few percent, you may well stop with apparent remaining range.
I really try to avoid going below 10%. It does the battery no good, power is limited, you have no buffer for unexpected detours, you may stop unexpectedly and you may be waiting a long time if you're planning on charging at a supercharger. In my opinion, there are few situations where it's worth the hassle/risk.
But of course, Tesla should do everything possible to ensure that the estimation for remaining available capacity is as good as possible. I think this is the reason why you often can drive below 0 miles. I think the BMS will basically say:"best-case, you can pull 70 kWh from the battery, worst-case around 68 kWh", and then 68 kWh is 0%/0 miles, and you have a 0-2 kWh zero mile buffer. If this estimator screws up by a few percent, you may well stop with apparent remaining range.
whitex
Well-Known Member
You must be talking ideal range, not rated range. Not sure idea range was ever speced. P85D EPA rated rage is 253miles at 100%SoC. What is your rated range at 100%SoC today?
iKhalid
Member
1. The 12v battery was complaining because the high voltage battery stopped feeding it. It lasted for 20 minutes until the screens depleted it.
whitex
Well-Known Member
That would make me think there is something wrong with the 12V battery. If the battery was full and drained in 20mins, that would mean the screens are drawing about 100A average current (1200W) since the battery is a 12V/33Ah battery. That is obviously not the case for the Tesla screens, which means the 12V battery has a lot less capacity than expected.
Why replying without fact? What those kind of qualitative statement brings in the discussion honestly? This is an arrogant comment.
So let's put things straight: considering a Model S 75D:
- m=2011kg
- q (density air) at 0°C = 1.2922kg/m3
- S.Cx= 2.34*0.24= 0.56m²
- rolling resistance coefficient = 0.015 (Cr at 50km/h) * (1+(0.006*delta V)²) (delta V beyond 50km/h) = 0.1513
So at 105km/h = 29.17m/s and 0°C, the Model S needs 18kW to keep speed constant.
Let's add 2 seat heater (1.5W/km) and HVAC at 23°C (3.5W/km) and you need to add 5W/km.
You can CLEARLY see that the power necessary is nothing crazy in winter compared even to summer and for a car that can deliver 300kW+ in term of power, I don't think 20kW is putting significant strain to the battery.
And NO, the car is not using "FAR more than 30kW" in winter at 0°C at 65mph constant.
You are ignoring the fact the battery uses energy to heat itself and ignoring the fact the battery is far more inefficient when cold.
I'm just going by my experience. Discount it however you'd like. It's only worth 2 red cents.
No, once the battery is "warm", it does not heat itself.
Even if it does, the battery heating is considered to take ~5,5kW and the cabin heating at the beginning also ~5,5kW.
So worse case scenario where you start with a car cold and right away go on the highway, the car will need the 20kW + 11kW of heating so 31kW. Which is quite logical as we can see that heating can add more 50% on consumption.
What is "battery" efficiency? What does it have to do with the energy necessary to move the car at a given speed?
The "issue" is that when the battery is cold, using a lot of current damage the battery. This is why the power is "limited" when cold. But obviously, at 30kW, you are just barely using 10% of the total power available...
hacer
Active Member
If yours is a software limited 60, then there is a good chance that it is caused by cell imbalance. With a software limit on the top end, there is no possibility for the user to balance by charging to 100%. I would expect that the service center should at least do a full charge/balance during the annual service for software locked cars, but who knows if they actually do. I also would expect that they would have observed the imbalance when you brought the car in and report that as the cause and but instead they say nothing is wrong. Something is wrong somewhere. It could be possible that if the battery was charged some before it got to the service center that could mask an imbalance but I would expect it to still be logged.
Johann Koeber
Happy Owner
That might have been me.
Before this experience, I often increased my speed when I was confident that the range was sufficient. I was thinking: why not have some fun close to the supercharger; refill will be fast.
On that day I was going maybe 180 (km/h, not miles). But it was also a lot of uphill. The battery was down to about 6 % of its range when the car shut down.
Roadside assistance was great. They explained to me that the battery was under stress (probably heatwise) so that it wasn't charging the 12V battery any more - for some time. I still had the first 12V battery and about 240,000 km on the odometer. So it might have been a bit weak anyway. I replaced it the next chance I had.
Moral of the story: Do not aim at arriving with less than 10 % range. If you do, then chill, slow down. If I had known what I know now, this would not have happened.
iKhalid
Member
I have a classic Model S with a true 60kWh battery; long before they introduced the 75kWh.
Estimating the state of charge is not an exact science. Nothing to do with Tesla. It’s a fact of life that affect all batteries to various degrees.
The battery management system can only try to predict how much is left. It can’t estimate it accurately. And any battery powered device needs to be treated as such.
A good read on the topic:
Measuring State-of-charge - Battery University
Pay attention to the part about coulomb counting.
If you Google SOC and coulomb counting you will realize that this is not a trivial and ‘solved’ issue. Measuring correct SOC is very challenging. Tesla is very good at getting it right, but with 250.000+ vehicles on the road? Someone will eat the flatbed trip from time to time.
Lesson? Don’t drive EV’s close to the red line unless you feel lucky.
The battery management system can only try to predict how much is left. It can’t estimate it accurately. And any battery powered device needs to be treated as such.
A good read on the topic:
Measuring State-of-charge - Battery University
Pay attention to the part about coulomb counting.
If you Google SOC and coulomb counting you will realize that this is not a trivial and ‘solved’ issue. Measuring correct SOC is very challenging. Tesla is very good at getting it right, but with 250.000+ vehicles on the road? Someone will eat the flatbed trip from time to time.
Lesson? Don’t drive EV’s close to the red line unless you feel lucky.
Shouldn't Tesla adjust their range estimators more conservative then?
What good is a low end of a range estimator where you can't go under 15% (or whatever number could be deducted from the experiences in this thread)?
I understand estimates changing over time, but going from 6% to shutdown makes the range estimate useless. Your story actually makes it sound like the battery could have been under stress at any percentage. Would this also have happened at 50%?
Then Tesla should include the 12V in the range estimation. If the car was not able to charge the 12V, it should let you know and put range at unknown as soon as it sees this.
But let's assume this really is a "less than 10%" issue. IMO there is no excuse at shutting down at 6% other than a component breakdown. If low-end estimates can't be sufficiently accurate, Tesla should not display them as they do.
As for 180 kph, well we all know Teslas are crappy autobahn cars.
The California dragstrip cars that they are...
It appears that these cases are infrequent, if not rare, based on this thread. So it’s quite possible Tesla has indeed adjusted to a more conservative estimate. Clearly many people have gone below 15% (me included) without shutdown.
Edit to clarify: I imagine there is a balance here. Tesla doesn't want owners stopping significantly sooner/more often than necessary; that would cause widespread inconvenience. Tesla also doesn't want owners running out of charge. If they choose to tilt the balance toward the conservative (technically allowing for a reserve below 0), I'm quite certain people will become more comfortable getting closer to or exceeding 0 mi/km remaining. This could result in similar or worse outcomes.
It is probably best for Tesla to be as accurate as possible and err slightly on the side of conservative. From what we know in this thread and forum, it appears to be a relatively successful strategy, aside from a few cases. This most certainly doesn't appear to be a widespread issue.
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@ohmman Sure, I could see Tesla wanting to present estimates in as good a light as possible, to the inconvenience of whatever number of people they can get away with - if that is what you are saying...
Frankly, my responses were more to the comments offered on TMC than to Tesla's actual actions in this. IF we assume it is correct to ask people to not drive under 10-15% as somehow a good solutiong to this, then seriously Tesla should change this estimate. That's IMO a big if. And a big ask. I don't agree.
However, I'm not convinced these instances are about the risks of driving under 10-15% at all. I think the speculation about 12V running out, for example, or other malfunction, sounds more plausible. In that instance Tesla really should just adjust their warnings to warn of this - those warnings might be separate from any range estimates.
Frankly, my responses were more to the comments offered on TMC than to Tesla's actual actions in this. IF we assume it is correct to ask people to not drive under 10-15% as somehow a good solutiong to this, then seriously Tesla should change this estimate. That's IMO a big if. And a big ask. I don't agree.
However, I'm not convinced these instances are about the risks of driving under 10-15% at all. I think the speculation about 12V running out, for example, or other malfunction, sounds more plausible. In that instance Tesla really should just adjust their warnings to warn of this - those warnings might be separate from any range estimates.
This nonnegative bias is always a pleasure to experience.@ohmman Sure, I could see Tesla wanting to present estimates in as good a light as possible, to the inconvenience of whatever number of people they can get away with - if that is what you are saying...
This nonnegative bias is always a pleasure to experience.
Well, the double smiley hopefully helped to put it in its cheeky (or mischevious) context.
But in all seriousiness, I don't think this particular case necessarily is a problem with Tesla's estimate algorithm, but an unrelated issue that causes a similar outcome, that could use better warnings. E.g. 12V battery issues.
I just had an issue with people blaming others for driving under 10-15% as somehow irresponsible. IMO that's uncalled for and one of those odd knee-jerk Tesla defense reactions that just becomes unnecessary victim blaming and shaming so often.
Seems you did not read the comment you were responding to. 180kmh it's no problem for the Tesla.As for 180 kph, well we all know Teslas are crappy autobahn cars.
The issue here is that on very low SOC, the voltage is lower so for a given power, you need more current. At 6%, the amount of power is limited. So if you go very fast, and uphill, it can be too much power draw.
I am sure you haha experience an ICE car starting to rattle or shutdown when there was one 0.5l remaining in the tank and going uphill because the fuel is pumped on a location of the tank where there was no enough fuel? But it would not mean that the car could not run in normal conditions with more fuel, right?
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