Battery degradation!?

[raviman8]

I have had my SR+ for almost 4 weeks now (June 7) ... I keep the battery daily charge set to 90% and charge with a NEMA 14-50. When I first got the SR+ it would charge to 345km. Almost 4 weeks later and now a 90% charge returns 338km... Not a big deal but definitely noticeable with a 7-8km drop.

Note no sentry mode enabled when at home.....


Thoughts?

 

[Tam]

...Thoughts?

It's guaranteed for 70% rentention for 8 years / 100,000 miles.

Comparing partial charged to partial charged status is not a very good comparison (50% to 50%, 90% to 90%).

To compare, you need to compare 100% to 100%.

Also, you need to take into calibration drift.

So, before comparing, you need to recalibrate your calculation: deplete your battery down then charge it up to 100%. Doing 1 time may not enough. You might need to do several times.

WARNING: Depleting your battery is not good for your battery longevity. It's worse than 100% charging. And...

100% charging is not good for your battery longevity either but at least you can drive your car to bring it down to 90%.

So in practice: Just enjoy driving your car and don't worry about it. If there's a 30% drop then it's reasonable to check it out.

 

[ucmndd]

Range is an estimate and fluctuates. 2% is “margin of error”. Move on and don’t obsess.

 

[ewoodrick]

Don't worry about it. Number of factors will change the numbers, none having to do with degradation. Make sure that you do charge to 100%, preferably with a long trip in front of you, every few months.

Just have fun in the car!

 

[raviman8]

good to know. thanks to everyone that responded. much appreciated.

 

[Rocky_H]

Make sure that you do charge to 100%, preferably with a long trip in front of you, every few months.

Disagree with that. Charging to 100% full does not help the battery; it's a little bit harmful to do often, so use it as needed, but it's not something to "make sure" to do. It does help tune in the software's estimation algorithm, so that gets it back into better accuracy, but that's a warm fuzzy feeling for you to make a pretty number, not something that is good for the battery.

 

[vickh]

Disagree with that. Charging to 100% full does not help the battery; it's a little bit harmful to do often, so use it as needed, but it's not something to "make sure" to do. It does help tune in the software's estimation algorithm, so that gets it back into better accuracy, but that's a warm fuzzy feeling for you to make a pretty number, not something that is good for the battery.

what about an SR. I believe the software lock "protects" it? I believe @GigaGrunt confirmed that in a different thread.

 

[dmurphy]

I usually leave the car at 90% Always plugged in when I’m home.

Today, I charged to 100% for the second time since getting the car 2 1/2 months ago. I was planning a long-ish trip today that ended up not happening, so it’s at 100% “for nothing.”

I’ll drive it down below 90% tomorrow, but based on the range, don’t think I have much to worry about. 309/310 = 0.00323%. Definitely within the margin of error.

 

[Sparky4life]

Take a look at how my rated range has fluctuated over time. It's not battery degradation (maybe 0.5% of it is), it's just the inacuracies in the capacity estimates by the BMS.

I almost always charge to 80%. The algorithm seems to self correct without the need for me to jump through hoops (i.e., charging to 100% or down to < 20%, etc.)

 

[Sparky4life]

Range is an estimate and fluctuates. 2% is “margin of error”. Move on and don’t obsess.

Based on my observations it's more like 5%.

 

[ucmndd]

Based on my observations it's more like 5%.

Yes, agree. What I actually meant was "2% is well within margin of error".

 

[VQTRVA]

Take a look at how my rated range has fluctuated over time. It's not battery degradation (maybe 0.5% of it is), it's just the inacuracies in the capacity estimates by the BMS.

I almost always charge to 80%. The algorithm seems to self correct without the need for me to jump through hoops (i.e., charging to 100% or down to < 20%, etc.)

View attachment 426130

I'm starting to believe this more & it appeared that 'jumping through hoops' may have had an adverse effect on my range recently post calibration.

My last sub 10% to 100% charge posted range from the car was 300 miles.
Then the subsequent 80% charge was 245 miles down from usual 249 miles.

In recent days the 80% charge has climbed to 253 miles with nothing but a 2019.20.4.2 update in between calibration & current displayed range.

 

[TheDon]

Sparky4life
What did you use to get the graph above? I am a new owner (1 month) and love the technical stuff as well as the car.

 

[Sparky4life]

Sparky4life
What did you use to get the graph above? I am a new owner (1 month) and love the technical stuff as well as the car.

https://teslafi.com

 

[scubastevo80]

Take a look at how my rated range has fluctuated over time. It's not battery degradation (maybe 0.5% of it is), it's just the inacuracies in the capacity estimates by the BMS.

I almost always charge to 80%. The algorithm seems to self correct without the need for me to jump through hoops (i.e., charging to 100% or down to < 20%, etc.)

View attachment 426130

I have a similar scenario for my LR AWD model 3. I bought my car in October and throughout the winter, range drifted down (according to Stats app) from 310 to about 304 at 6500 miles in April. When the weather warmed up, Stats started showing me around 308+/-. (7000-9000 miles on the odo). Two software updates ago, my max dropped to about 302 miles of range. I charge to 85% or 90% twice a week and typically run the car down to about 20-30% battery. I don't believe this to be true degregation, but rather Tesla limiting the top 2% for battery longevity or some other reason.

As a sidebar, I know the phantom degregation was reported for Model S cars (not Model 3). My wife's 2015 Model S 85D shows a max of 268 miles (of 270) at 45k miles on the odo, so no issues for her car.

 

[MaryAnning3]

but that's a warm fuzzy feeling for you to make a pretty number, not something that is good for the battery.

This is the truth. warm fuzzy feeling and not good for your battery