Mid Range Battery Math

[AlanSubie4Life]

So it seems your battery is ok after all. If we take the 62kWh as a reference new - 2.6kWh Buffer we have about 1-2% Degradation. This is what most Teslas Model 3 have in the first few months

This is incorrect. Remember that the 58.4kWh includes the buffer. (See this Capture you provided showing how it works...)

So it is 58.4/62.5 = 6.4% degradation. (He’s at something like 247 rmi vs. 264 rmi when new!)

SOC UI is a value read by the CAN. It is a calculation of nominal full pack*SOC UI = nominal remaining.

That’s what I thought. But how come:

58.4kWh*0.851 = 49.7kWh? (This is not the same as nominal remaining in the capture...)

 

[ran349]

SOC UI is a value read by the CAN. It is an internal calculation of nominal full pack*SOC UI = nominal remaining.

SOC is calculated by Amund and is Nominal full pack * SOC % = expected remaining. What the car shows.
I think he uses nominal remaining in some versions, but I found it to be wrong, it has to be expected remaining.

Please note that the car uses expected remaining to calculate the SOC and not nominal remaining. Most of the time when the battery is warm these two values, nominal remaining and expected remaining will be the same, but very often they are not.


So it seems your battery is ok after all. If we take the 62kWh as a reference new - 2.6kWh Buffer we have about 1-2% Degradation. This is what most Teslas Model 3 have in the first few months.

That's interesting. I know for my car, the correct value to use to match car SOC% is ideal remaining, not nominal, or expected remaining. This comes from TM-Spy data. It could be that it is done differently for model 3 than for model S cars. Or that the variable labels for TM-Spy are different than for Scan My Tesla.
Could you post some results to show that?

 

[TimothyHW3]

That's interesting. I know for my car, the correct value to use to match car SOC% is ideal remaining, not nominal, or expected remaining. This comes from TM-Spy data. It could be that it is done differently for model 3 than for model S cars. Or that the variable labels for TM-Spy are different than for Scan My Tesla.
Could you post some results to show that?

That is correct. Ideal and expected show the same value most of the time, if not all(on my Model 3 all) I have screenshots where ideal=expected<1kWh than nominal remaining.
This happens when the battery is cold, below 10°

 

[TimothyHW3]

This is incorrect. Remember that the 58.4kWh includes the buffer. (See this Capture you provided showing how it works...)

So it is 58.4/62.5 = 6.4% degradation. (He’s at something like 247 rmi vs. 264 rmi when new!)

Yes, I just came to correct myself on that one.

If we so the math with 150 it is even 63kWh.

That is indeed a high degradation for such short time. Maybe he is suffering from that 60-80% 70-90% "every day-always plugged in" charging bug.

Could you please let us know if you charged 60-80/90% daily and had the car plugged in all the time?

 

[ran349]

That is correct. Ideal and expected show the same value most of the time. I have screenshots where ideal=expected<1kWh than nominal remaining.
This happens when the battery is cold, below 10°

Ok, but I found that when ideal and expected were not the same value, it was ideal that actually matches the car SOC.

 

[AlanSubie4Life]

Nominal full pack * SOC % = expected remaining.

How come this formula also does not work here? Is the SoC always rounded to the nearest 0.5% or something?

 

[AlanSubie4Life]

Maybe he is suffering from that 60-80% 70-90% "every day-always plugged in" charging bug.

Could you please let us know if you charged 60-80/90% daily and had the car plugged in all the time?

I’m not saying this is real degradation (though it might be), but I really am beginning to believe there is no charging regimen that spares you this type of loss. It seems to be happening to nearly everyone to some extent or another. I don’t believe there is any magic formula. I am not saying the BMS can’t get confused, but I don’t believe that’s the reason for all these issues. Maybe there is an underlying software issue or something, but I don’t think whatever it is can be avoided.

I’m at 3.3% “degradation” after a year, and it does not seem to matter how deeply I discharge, what I charge to, etc. My range is on a downward spiral, as surely as the sun rises in the morning.

I just don’t think it is worth spending any time to try to make your range recover - nearly all the reports I see indicate such efforts usually do nothing.

 

[TimothyHW3]

Ok, but I found that when ideal and expected were not the same value, it was ideal that actually matches the car SOC.

I have to observe it. Looking at my screenshots from SMT they are always matching, even when there is a 1.5kWh difference between nominal and expected. Could it be that the IOS app delivers different CAN Bus values and calls them the same as SMT?

 

[hugh_jassol]

That is indeed a high degradation for such short time. Maybe he is suffering from that 60-80% 70-90% "every day-always plugged in" charging bug.

Could you please let us know if you charged 60-80/90% daily and had the car plugged in all the time?

My daily routine is between about 70-90% for the first 3 months of ownership, then I switched to 60-80% for the next 6 months or so. When I started to see the big drop in rated range, I went back to 70-90%. My car is set to charge at 8pm daily, so while it's always plugged in when home, it only charges once a day. Come to think of it, back for the period of time where I was getting my rated 264 (for about the first 4-5 months), I had it charging every time I plugged it in... I wonder if that could make a difference?

So it is 58.4/62.5 = 6.4% degradation. (He’s at something like 247 rmi vs. 264 rmi when new!)

For the past week or so, it's been about 243 rmi... but just with yesterday's charge, I was up at 246 rmi, which is the highest it's been since the first week of Dec. (note that in my most recent screen capture of SMT, my "Nominal Full Pack" was 58.4 kWh, which was up from 57.8 kWh the day before).

’m not saying this is real degradation (though it might be), but I really am beginning to believe there is no charging regimen that spares you this type of loss. It seems to be happening to nearly everyone to some extent or another. I don’t believe there is any magic formula. I am not saying the BMS can’t get confused, but I don’t believe that’s the reason for all these issues. Maybe there is an underlying software issue or something, but I don’t think whatever it is can be avoided.

Yes, I too tried the <10% -> 100% three times to see if I could get it back, but it made no difference.

 

[TimothyHW3]

I’m at 3.3% “degradation” after a year, and it does not seem to matter how deeply I discharge, what I charge to, etc. My range is on a downward spiral, as surely as the sun rises in the morning.

.

Yeah, but his degradation is more than 5-6% after only 16000km. Especially at 99% AC charging.
I would say this is not normal and is probably a messed up BMS due to the always plugged in bug. Would be great if he can chime in and deliver more data on his habbits.

My daily routine is between about 70-90% for the first 3 months of ownership, then I switched to 60-80% for the next 6 months or so. When I started to see the big drop in rated range, I went back to 70-90%. My car is set to charge at 8pm daily, so while it's always plugged in when home, it only charges once a day. Come to think of it, back for the period of time where I was getting my rated 264 (for about the first 4-5 months), I had it charging every time I plugged it in... I wonder if that could make a difference?

Well, I have been saying numerous times that this charging behaviour 60%-80% and 70-90% daily messes up the BMS, but nobody believes me. To me this is the culprit on Model 3 and I am yet to find an owner who doesn't suffer from loss of range due to this behaviour. We have at least 20 reports just in this forum alone.

Try charging from 10/20%-90% a couple of months - meaning don't plug it in before you go below 20% and make sure to time it so that you get to 90% and drive right away - see if it improves the BMS a bit. Or if you can persuade Tesla to reset your battery's BMS and then charge 20%-90% and see how that goes.

 

[hugh_jassol]

I would say this is not normal and is probably a messed up BMS due to the always plugged in bug. Would be great if he can chime in and deliver more data on his habbits.

I think we posted at the same time - see my habits in my prev post

 

[TimothyHW3]

I think we posted at the same time - see my habits in my prev post

Yes, just replied - I think switching to 20%-90% for the next couple of months could bring back the range a bit.

 

[hugh_jassol]

Well, I have been saying numerous times that this charging behaviour 60%-80% and 70-90% daily messes up the BMS, but nobody believes me. To me this is the culprit on Model 3 and I am yet to find an owner who doesn't suffer from loss of range due to this behaviour. We have at least 20 reports just in this forum alone.

Except.... there are just as many who charge daily with no issue.

Try charging from 10/20%-90% a couple of months - meaning don't plug it in before you go below 20% and make sure to time it so that you get to 90% and drive right away - see if it improves the BMS a bit. Or if you can persuade Tesla to reset your battery's BMS and then charge 20%-90% and see how that goes.

I will try this and see how it goes. Do you think supercharging would make a difference?

 

[ran349]

For the past week or so, it's been about 243 rmi... but just with yesterday's charge, I was up at 246 rmi, which is the highest it's been since the first week of Dec. (note that in my most recent screen capture of SMT, my "Nominal Full Pack" was 58.4 kWh, which was up from 57.8 kWh the day before).


Yes, I too tried the <10% -> 100% three times to see if I could get it back, but it made no difference.

How did you calculate this 246 value? Because, if in fact your constant is 236, you should have had 247 rated miles; 58.4/.236 = 247.46.

 

[TimothyHW3]

Except.... there are just as many who charge daily with no issue.

How do you know? Most people keep the car on % and never charge to 100% to see what the value is...
I would estimate that some are more effected than others, but probably all are affected. It is too many reports to be ignored.

I will try this and see how it goes. Do you think supercharging would make a difference?

Well, you don't supercharge at all so that shouldn't be an issue . Even if you supercharge from time to time shouldn't matter as long as you don't top up just 60-80%.

 

[AlanSubie4Life]

Yeah, but his degradation is more than 5-6% after only 16000km. Especially at 99% AC charging.
I would say this is not normal and is probably a messed up BMS due to the always plugged in bug. Would be great if he can chime in and deliver more data on his habbits.

Yet, we have fleet data that looks like this for the LR RWD and AWD (credit @KenC and the Stats app), showing that 6% “degradation” is within the normal distribution (though modestly towards one tail). Not an MR, but presumably the behavior of that very small fleet is similar, and aging may be slightly accelerated with a smaller battery, given the same number of miles accrued. Both time and discharge cycles are factors of course:

 

[hugh_jassol]

Yet, we have fleet data that looks like this for the LR RWD and AWD (credit @KenC and the Stats app), showing that 6% “degradation” is within the normal distribution (though modestly towards one tail). Not an MR, but presumably the behavior of that very small fleet is similar, and aging may be slightly accelerated with a smaller battery, given the same number of miles accrued. Both time and discharge cycles are factors of course:
View attachment 494159

Wonder if they can publish the MR stats, even if it’s just a few

 

[hugh_jassol]

How did you calculate this 246 value? Because, if in fact your constant is 236, you should have had 247 rated miles; 58.4/.236 = 247.46.

Rated miles displayed / batt percent remaining

 

[AlanSubie4Life]

Rated miles displayed / batt percent remaining

These values are all so close that it is hard to know given the number of significant figures available. That calculation will be more accurate the higher the SoC, in any case. Constant is around 236Wh/rmi or 237Wh/rmi, and your rated range with a warm battery is around 246 or 247 rated miles. Very hard to be more precise than that. It is all pretty consistent with your 58.4kWh with that same warm battery - the uncertainty is around 0.5%.

 

[3Victoria]

I have seen suggestions that one needs to charge to 90% and leave connected for 6h to let the car balance the cells. It would be nice to get some definitive info from Tesla.