Ladeempfehlung Kurzstrecke

Infos zu Batterie und Ladung des Model 3...

Re: Ladeempfehlung Kurzstrecke

von citizenY » 29. Aug 2019, 10:44

pco hat geschrieben:Weiss nicht wo in deinem Beitrag die "Frage" ist....

Sie war vielleicht nicht sauber ausformuliert. ;)

Ich habe in den Einstellungen die Anzeige auf "Prozent" stehen, nicht auf "Reichweite". Wenn das BMS nun "durcheinander kommt" bemängeln viele ja scheinbar eine zu niedrig angezeigte Restreichweite. Das tangiert mich nicht, da ich ja nicht die Restreichweite anzeigen lasse. Stimmt denn immer :!: die prozentuale Anzeige oder weicht diese dann auch ab und zeigt einen zu hohen Ladestand?

lostpanda hat geschrieben:You can always charge 90% on weekends (or occasionally to 100% at Ionity Chargers) which will restore the misscalculation of BMS

(Another advantage: you'll get warmed up every morning and with full regeneration capacity)

And one can charge to 90% or occasionaly to 100% at Ionity chargers to restore the BMS readings.

I have yet to receive my Model 3, probably end sep, and I will be charging primarily on Schuko in the office,,konstenlos.. :D

Thanks for your comment and calculation. I am fully aware that I could charge up to 80% during the night. My question was more related to the misdiagnosing BMS, especially if the BMS only wrongly calculates remaining range or also remaining battery capacity in %.
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Re: Ladeempfehlung Kurzstrecke

von lostpanda » 29. Aug 2019, 11:48

Hi citizenY

now the question is clear (Sie war vielleicht nicht sauber ausformuliert) which you wrote in last lines of your recent comment. :D

Following is my rough understanding on the matter and I would just like to share. If you are having different opinions, do share.

Based on my understanding from the videos and in general about Li-Batteries, the battery voltage is always a primary indicator of extent to which a battery is charged (State of charge) https://siliconlightworks.com/li-ion-voltage. Ratio of the current voltage of the battery to the maximum prescribed voltage for the battery will give the percentage to which it is charged. (As it is option 1 available in m3, near the battery symbol https://insideevs.com/news/338225/simple-ways-to-extend-your-tesla-model-3-battery-life/). So I believe the battery percentage cannot be wrong because BMS cannot be erroneous in reading a voltage value, otherwise there will be fire all around.


Now anyone can make (not only Tesla) a table showing Battery Percentage Vs. Range. For example, if the battery is at x%, just drive it until 0% and note down the kms travelled. I think this is option 2 available in m3, which is also shown near the battery symbol.
But if you noticed, this estimation does not take into account variables such as driving habits, terrain, etc. So I believe the battery range is prone to false values.
https://www.businessinsider.de/tesla-infotainment-system-best-in-world-beats-bmw-consumer-reports-2019-5?r=US&IR=T

However, when you take all the variable factors also into account, you get dynamically updated range which m3 shows on graph and updates frequently https://www.inverse.com/article/50894-tesla-model-3-charging-without-charger. But is this always correct? Yes and No, because this extrapolation is based on recent inputs (like driving behaviour, temperature etc) but car doesnt know what is going to happen in next minutes (should you drive behind a bus or truck :D ) ? That is why people find this method helpful than the first option and definitly the second option.


The bolded text might be what you were looking for and
although, method 2 and 3 need not to be explained here but for some reasons, I felt like explaining these will avoid any missing information.
 
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Re: Ladeempfehlung Kurzstrecke

von Helmilectric » 29. Aug 2019, 12:06

@lostpanda while the voltage generally is a good indicator BMS in general usually work with their "experience" with that special battery meaning that a BMS usually knows about the charging cycles and how far it drove to lose a certain amount of energy. At least this is how it is known from e.g. cell phones and I would assume there's some similar stuff in an EVs BMS.

It is a known issue on for example iPhones that if you often charge them for example from like 60-80 only or just don't watch your charing at all that they might over time drop battery lifetime as shown on the display. A "reset" of the BMS or that faulty behaviour is done in a similar manner as described in this thread: Use it down till it shuts off, charge it to 100% - if it's still not good enough repeat this cycle a few times. This usually brings back significant runtime (apart from general battery wear of course).

Of course it's way harder to the same (total discharge) on a car but the procedure given by Tesla to Kim in the video sounds the same to me. I'm also not sure why BMS' work that way - most likely it's because the voltage isn't a stable indicator over the lifetime of a battery and the voltge-to-chargelevel comparison might not work identical through that lifetime.
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Re: Ladeempfehlung Kurzstrecke

von lostpanda » 29. Aug 2019, 14:11

H3LMI hat geschrieben:how far it drove to lose a certain amount of energy


Even in 2019 when we want to put everything on single chip, it is not imaginable that why a BMS would have to log the kms driven and perform calculations for available range or perform relatively complex calculations for dynamic range.
Are those calculations not kept for some relatively powerful chips of m3? Or Autopilot processing could have been driven from BMS itself ?

Lets move on to wiki https://en.wikipedia.org/wiki/Battery_management_system and try to find where it specifically mentiones that BMS reports back available kilometer or iphone usage time. If you couldnt find, its okay, because BMS is not designated as a means of performing secondary calculations in any device.

I think you missed my point from the previous post by a large margin. Let me try this way.
The BMS communicates back the voltage level or voltage percentage or SoC to M3 or your iphones Ax processor. You may call this Primary Calculations
What to make out of that information, depends on M3 central computing or your Iphones Ax Chip etc. And this is a Secondary Calculation which if you read wiki, BMS is not entitled to do.
 
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Re: Ladeempfehlung Kurzstrecke

von citizenY » 29. Aug 2019, 15:32

lostpanda hat geschrieben:Based on my understanding from the videos and in general about Li-Batteries, the battery voltage is always a primary indicator of extent to which a battery is charged (State of charge) https://siliconlightworks.com/li-ion-voltage. Ratio of the current voltage of the battery to the maximum prescribed voltage for the battery will give the percentage to which it is charged. (As it is option 1 available in m3, near the battery symbol https://insideevs.com/news/338225/simple-ways-to-extend-your-tesla-model-3-battery-life/). So I believe the battery percentage cannot be wrong because BMS cannot be erroneous in reading a voltage value, otherwise there will be fire all around.

This actually solves my issue. If battery percentage is always displayed correctly I do not care about secondary calculations just to display typical range or range based on average consumption of last 10/25/50 km.

H3LMI hat geschrieben:@lostpanda while the voltage generally is a good indicator BMS in general usually work with their "experience" with that special battery meaning that a BMS usually knows about the charging cycles and how far it drove to lose a certain amount of energy.

This contradicts lostpanda's explanation of the BMS always showing the right charging percentage based on the battery voltage. Although if the BMS would work that way it would show really inaccurate figures considering range and battery charge in %.
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Re: Ladeempfehlung Kurzstrecke

von Helmilectric » 29. Aug 2019, 15:40

Well maybe I was unclear. I don't pretend to know what exactly Tesla or Apples iPhone BMS does and I don't think we can find that by looking at Wikipedia. What I was meaning to say is that there are most likely other factors taken into account - my opinion only obviously as I don't have any insights. And indeed the behaviour on other system shows something similar. On an iphone of course there's no distance to go and also not a time prediction that tells you how long your battery is supposed to run. There's only that percentage thing and I can quite surely say that this is not only read from the voltage - otherwise it wouldn't show this misbehaviour. Again, this is not an EV, not Tesla so it's just a side comparison.

Tesla may do things differently and percentage might always show the right values while only remaining distance shows errors and I can't even deliver any facts here as I don't own a car to test it. I will definitely once the car is here as I will definitely test using a lower SoC at first and see how this changes what BMS shows and what really comes out of the car in terms of drivable distance.
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Re: Ladeempfehlung Kurzstrecke

von citizenY » 29. Aug 2019, 16:20

H3LMI hat geschrieben:Tesla may do things differently and percentage might always show the right values while only remaining distance shows errors and I can't even deliver any facts here as I don't own a car to test it. I will definitely once the car is here as I will definitely test using a lower SoC at first and see how this changes what BMS shows and what really comes out of the car in terms of drivable distance.

I know that all we are discussing on the BMS is based on a wild guess. My only concern is if I can rely on the values stated in the car, especially the battery charge. If you did some testing please share your insights. I only own my Model 3 for a week now and actually don't know how to put our hypothesis to the test.
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Re: Ladeempfehlung Kurzstrecke

von lostpanda » 29. Aug 2019, 17:04

H3LMI hat geschrieben:Well maybe I was unclear. I don't pretend to know what exactly Tesla or Apples iPhone BMS does and I don't think we can find that by looking at Wikipedia.

At least it was sufficient enough to educate one to understand the scope of using term "BMS" and to understand what is expected and achieved using this BMS.

H3LMI hat geschrieben:iphone of course there's no distance to go


You were more interested in bringing iphone here. I use open-source. But...
BMS, if used all alone, is going to show you the voltage of the cells as it is.
But if you combine BMS with fancy software and then find out something is wrong with battery percentage, then please dont blame BMS atleast.
Here is something for your laugh: https://www.thejournal.ie/iphone-battery-percentage-bug-2553853-Jan2016/


Now you can have a good amount of feeling that BMS is not to be blamed, but the fancy software (middle-man) which controls the readings of BMS before showing it to you.
 
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