What Percent is Your Tesla Charged to While at Home?

[DrChaos]

If AAKEEs most recently posted science paper on calendar aging carries over, then 80% may be the worst for NCA, worse than 90% or 100% for calendar aging. It's also the most common result on the poll now. (though cyclic aging near the top is bad too).

Personally I now do 50% limit most of the time. Infrequent 90-100% for travel. It's inconvenienced my life exactly never. Performance at 50% is just fine.

Every once in a while, a charge to 80%+ and then a few days of normal driving without charging to help recalibrate the BMS, charge up again when < 35%. Improved range estimates.

I have 348-350 / 358 miles after 11 months, with no clear degradation last 6 months. The science works. I really appreciate reading all the info here, it changed my behavior for sure and I think it's working. If the sqrt(t) degradation model holds up, then avoiding the high degradation in the first year is very important and will continue to have benefits for years to come.

 

[DrChaos]

He can’t tell people only charge to 50% because general public will freak out and anti-EV pundits would have a field day saying you can’t charge your EV more than 50% so they are useless.

And in 2018 maybe not all the papers on calendar aging were out and published. Not that Elon would particularly know or follow them; he'd go by his personal gut or what someone once vaguely told him.

 

[M3P Heavy]

I am doing the exact same thing with my new NCA M3p but at 55% as per the thread recommendations. I have the exact highway commute and lose about 10% each way as well - coming home with 30% works great!

Tessie is a paid app but it’s pretty great for more in depth graphs/data exploration! My goal is to stay way above the fleet average as it is right now

Agreed! I'm not saying what is best for anyone else, but having a 48 amp wall connector I can recapture whatever I need pretty quickly if I have to up the charge. 55% for me leaves me more than enough range to do anything extra I need after work and still enough to do an entire extra commute if I forgot to charge.

I think a reasonable way to think about it is just charge to the lowest % that meets your range needs, charging availability, and keeps you from having range anxiety. Might be 50 for some and 90 for others, do what works for you!

 

[KenC]

90% as at 80% the car is not able to balance well. I am at 5+ years and 108,000+ miles and still at 95% of new.

View attachment 936471

How do you check your cell balance?

 

[zoomer0056]

I am doing the exact same thing with my new NCA M3p but at 55% as per the thread recommendations. I have the exact highway commute and lose about 10% each way as well - coming home with 30% works great!

Tessie is a paid app but it’s pretty great for more in depth graphs/data exploration! My goal is to stay way above the fleet average as it is right now

Hard to tell, but that looks like 2 charge sessions in 11 days? I Also use Tessie, I like it a lot.

 

[dhrivnak]

How do you check your cell balance?

I do not know on the model 3. As I learned that from my Roadster years. And fortunately the Mosel 3 is holding up well for me.

 

[dafish]

But Elon says 90% or 95% are fine! And no reason to go below 80%. Who are you going to believe?

Now I am just causing problems, adding no value (as is typically the case when posting ElonTweets).

View attachment 936494View attachment 936495

And using them out of context as well. Elon has been challenged on those posts, and has clarified that he said "not worth" as a convenience to his life, and that indeed there was damage done, even at 80%. One just has to read a bit more. I believe I have links to his clarifications in this document:

EV Wiring Project.pdf

drive.google.com

Who am I going to believe? Researchers first, and those, Akee as an example, that spent time digging into same.

 

[m3p-ev]

Hard to tell, but that looks like 2 charge sessions in 11 days? I Also use Tessie, I like it a lot.

1.5 charge cycles so that sounds about right (3 days driving) - way too early to tell but have been charging 55% from when I got it at ~50kms (80% SOC), now ~380kms.

Interestingly it also sat in the cold since its April build date at the SC at 40% SOC. Only reason I know this is because I drove up to check it out and my phone connected to the car by itself so I basically just checked up on battery levels until they disconnected it LOL.

Will keep tracking!

 

[AAKEE]

But Elon says 90% or 95% are fine! And no reason to go below 80%. Who are you going to believe?

Now I am just causing problems, adding no value (as is typically the case when posting ElonTweets).

In fact Elon is very right with all these statements but they will not reduce the degradation to a minimum.

 

[Apprunner]

Agreed! I'm not saying what is best for anyone else, but having a 48 amp wall connector I can recapture whatever I need pretty quickly if I have to up the charge. 55% for me leaves me more than enough range to do anything extra I need after work and still enough to do an entire extra commute if I forgot to charge.

I think a reasonable way to think about it is just charge to the lowest % that meets your range needs, charging availability, and keeps you from having range anxiety. Might be 50 for some and 90 for others, do what works for you!

FWIW, I don't think it matters charging to 60%. The 55% number is related to an average SoC for the battery. Charging to 60% and going to work where it sleeps at 50% all day is practically the same thing.

 

[AAKEE]

FWIW, I don't think it matters charging to 60%. The 55% number is related to an average SoC for the battery. Charging to 60% and going to work where it sleeps at 50% all day is practically the same thing.

The 55% number is not related to an average SOC but an fixed SOC, or actually the central graphite peak, that is at 57-58% (True) -soc for an panasonic NCA cell. I have used the term average SOC, but mainly to try to explain this in easy terms.

This picture shows the calendar aging vs SOC, time and temperature. There is no measuring points between 55 and 60% so the line is approximate, and do not reflect the real very close.
The central grafite peak is at 57-58% on a new panasonic NCA cell so its wise to stay below that number.
55% displayed SOC on a model 3/Y is 57% true SOC (because of the buffer be.low 0%) so the 55% is thoroughly chosen to find the maximum SOC level below the central graphite peak.

The central graphite peak moves up in SOC from calendar aging by time, and it also moves slightly downwards from cycles and faster downwards from fast charging. The easy way is to assume that it in total stays about at the same position during the life in a car.

 

[dafish]

I assume (and we all know what that means) that there at least can be some variation in test results as a result of test methodology, minor product differences and etc. Ergo I don't over-react to any one set of data. Taken as a whole though, it's clear we can certainly optimize our results by avoiding highish SoC.
Nor would I freak out if I need to be at 68% for peace of mind. The critical things to me are:

* Don't be one of those guys charging to 100% at each charge
* Don't live on super-chargers to save a few bucks.
* Aside from that enjoy the car.

Beyond those biggies I've some simple guideline I've adopted:
* Adopt a daily charge policy that's as low as possible and still meets use case demands plus whatever reserve you need for peace of mind between first available charging opportunities.
* Charge back to my baseline whenever possible.
* Departure charge when possible (and it usually is).

Do I charge to 50% as my baseline as it appears to be the safest high-ish value? Yep. Why not? It causes me zero problems But if it did would I charge to 65% if I needed that for peace of mind? Yep!

I don't see a "this is the right answer". I do think a lot of folks could mimic the above and be just fine, but this ain't life and death.

All the best,

-d

 

[m3p-ev]

Thank you @AAKEE for providing the literature backing these best practices.

What about the rate at which the charge is applied - say charging 12 hours to 55 on level 2 vs charging 4 hours to 55 on level 2?

Would this have any long term effects on degradation? I.e. could the level 1 have a slight advantage due to the slow trickle charge?

 

[AAKEE]

Thank you @AAKEE for providing the literature backing these best practices.

What about the rate at which the charge is applied - say charging 12 hours to 55 on level 2 vs charging 4 hours to 55 on level 2?

Would this have any long term effects on degradation? I.e. could the level 1 have a slight advantage due to the slow trickle charge?

Any AC charging is considered ”slow charging” and there is no win to reduce the charging power for that reason.

If we think in “charge late” terms, maximum AC charging speed 11kw and start the charging much shorter before the drive will reduce the time at higher SOC. This is specially valid above 55% for NCA (and above 60% for NMC and above 70% for LFP).

 

[3sr+buyer]

Any AC charging is considered ”slow charging” and there is no win to reduce the charging power for that reason.

If we think in “charge late” terms, maximum AC charging speed 11kw and start the charging much shorter before the drive will reduce the time at higher SOC. This is specially valid above 55% for NCA (and above 60% for NMC and above 70% for LFP).

Also, slower AC charging rate means that charging will become more costly, because the car is "turned on" while charging, which costs around 0.4kW.

Voltage	Amperage	Charge power (kW)	Percentage loss due to 0.4kW to keep the car on	Notes
240	48	11.52	3.5%	Wall Connector maximum; hardwired
240	40	9.60	4.2%	6-50 or 14-50 receptacle maximum
240	32	7.68	5.2%	Mobile Connector maximum; 6-50 or 14-50 receptacle
240	24	5.76	6.9%	10-30 or 14-30 dryer receptacle maximum
240	16	3.84	10.4%
120	16	1.92	20.8%	5-20 receptacle maximum
120	12	1.44	27.8%	Common 5-15 receptacle maximum (lower if shared with other receptacles drawing significant power)

 

[AAKEE]

I assume (and we all know what that means) that there at least can be some variation in test results as a result of test methodology, minor product differences.

The differences is not big (but very small.) There is some differences, like the degradation at very high SOC.
More or less all research shows that calendar shing is not much higher at 90-100% than at 70-80% at normal temperature.
In some research we see lower calendar aging at 100% than at 80-90%.

Otherwise, the differences is very small.
For our needs, what happens at 100% is not important for most people. We know from these numerous tests that the ”You need to drive asap after a 100% charge otherwise the battery get hurt” is a myth.

The degradation charts show very clear that we should stay below 55% displayed SOC(for NCA), and that having more than 60% in principle doubles the degradation.

This is from a actual Tesla model S cells test (removed from a 6 month old M S):

The total time for these tests was not specified but I did calculate the time for the Two cycles step tests and it seems to be about 6 months, or so.
Putting for example SOC80/25C step 2 (2.8%) time adjusted on one of the calendar aging charts i use most, the most of the others fit perfect on the chart as well.
25C at 50% and below is slightly below the expected from the charts but as the cells comes from used Model S we can assume that is was charged to 70-90% andbin turn we actually would expect a slight recovery from setting the cells at low SOC.

For calendar aging I would say that the case is closed, we have data enough to understand it very precise and even predict how a cars with a known capacity will degrade in the future.

 

[Resist]

Okay so, right now my 2018 LR Model 3 is battery is 50% charged and has been for almost a week, I haven't needed to drive anywhere with it. Today I'm going on a 3 hour trip. Should I charge to 80% before leaving or leave with 50% and make several short stops along the way for a 5 or 10 minute charge? There are plenty of Supercharging stations along my route. Then of course there is the drive back. Or at this point even worry about it anymore, as I'll never get the original 310 miles of range back. Right now the Stats app shows my max range right is 281 miles. My range went down a bit because last month I took a long 8 hour trip and pushed my speed, so that dropped my range on the app. My hope is to at least get my range back to around 290 miles, if I drive conservatively. The last time I even got 300 miles of range was around 11,000 miles ago.

 

[AAKEE]

Okay so, right now my 2018 LR Model 3 is battery is 50% charged and has been for almost a week, I haven't needed to drive anywhere with it. Today I'm going on a 3 hour trip. Should I charge to 80% before leaving or leave with 50% and make several short stops along the way for a 5 or 10 minute charge?

Either way is OK.
Cycles is a small part of the wear so do what is most convenient.

 

[AAKEE]

Lost in the sands of history at this point. Hard to know what happened with your specific vehicle but at least you know the capacity now.



1) this was an increase to 325, not 335.
2) it applied only to Model 3 LR RWD 2018/2019. Not Ken’s car. (AWD)
3) It did not appear to increase available capacity or change the constant. I assume this means the buffer was reduced, or another possibility is that the degradation threshold was increased from 72.5kWh to 76kWh. Hard to know without SMT reads in those early days exactly how it was done. But some owners have some energy graph pictures showing rated line at 239Wh/mi (corresponding to 234Wh/mi) prior to the change, allegedly.
4) There were some efficiency changes but not sure they were really connected. Recall that the initial EPA test results were voluntarily reduced (from either 325 or 335; don’t remember - would have to check docs).

I guess it was the same battery in the RWD LR as the 4WD LR (77.8kWh)?

Was the maximum range 325 milies?
What is the charging constant of that version?

Asking because of a Tessie wrong values situation (again).
I would guess the LR RWD had the same initial capacity as the other LR’s

 

[AlanSubie4Life]

I guess it was the same battery in the RWD LR as the 4WD LR (77.8kWh)?

Was the maximum range 325 milies?
What is the charging constant of that version?

Asking because of a Tessie wrong values situation (again).
I would guess the LR RWD had the same initial capacity as the other LR’s

Yes same pack (in reality some wiring differences at some point because of single motor).

234Wh/rmi (apparently never changed)
Degradation threshold 76kWh
So max range 76kWh/234Wh/rmi = 325rmi

SMT read says 77.8kWh full pack when new AFAIK.

The only thing that is not 100% clear is what the situation was when the car displayed 310 rated miles new. (But note that the EPA results were similar to the AWD version in terms of extracted energy - and also it got 335 miles or so in the EPA test (my recollection - anyone can check the docs).)

That’s why I think it was just a degradation threshold adjustment when they changed from displaying 310 miles to 325 miles. But just a guess.