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Battery capacity loss and weird fluctuation.

alexgr

Member
Aug 13, 2019
650
531
Tulsa
I have LR M3 of 08/19 with 15k on it now. Original range was 310 miles. Now, since about 10k, it is between 285 and 290 miles (7-8% loss that seems to be way more than average at this mileage). I read the "restore your battery" sticky thread and I am keeping my car in my garage overnight at various SOCs from 15% to 90% with charger unplugged (with no effect so far).

I have noticed that when I leave my car to sleep and even with no cable attached, the mileage sometimes increases (!) by as much as 10 miles spontaneously (along with %). I have observed increases from 50 to 53 miles, and approximately from about 160 to 170 miles and from 220 to 230. Several times I have consistently observed a mileage decrease after charging from ~140 to ~130 miles in a matter of 2 minutes.

I haven't seen anything like this reported on this forum yet. Any thoughts?
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,673
11,637
San Diego
Several times I have consistently observed a mileage decrease after charging from ~140 to ~130 miles in a matter of 2 minutes.

I haven't seen anything like this reported on this forum yet. Any thoughts?

That’s weird. @insaneoctane has an issue where his rated range will decrease or increase significantly with decay after parking, but I haven’t seen anything instantaneous as you describe. His issue happens over a couple hours instead.

To some extent it is normal to see range changes while parked, over time, in response to temperature changes, but they would not happen instantaneously as you seem to describe. And usually (not always) it would be decreases, not increases.

Kind of sounds like confused BMS, but we would need more info on how temperature is changing, how fast this happens (can you take video or a few pictures showing the rated miles vs time?), how frequently it happens, etc.

In general your overall range loss is pretty normal (7-8% is well within normal for that age and mileage though certainly a low percentile result), but this fast fluctuation issue is somewhat separate from that.
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
There is, of course, no way these changes indicate a real energy gain or loss. They are the apparent voltage/calibration issues. I have observed these ~10 miles gains before but the charging cable was plugged in overnight and I thought that it was simply some overcharging after charging restarted sometime in the night. I was VERY surprised when I saw the same overnight mileage gains with no cable attached. The temperature changes were near zilch as the car was in garage all the time at about 65F.

The drops near 45-50% SOC happened right after charging was done. Basically, my phone tells me the charging is complete at 145 miles, I go to the car right away (no more than 2 minutes) and see that it is at about 135 miles (and the app confirms that it is at 135 miles now, and % dropped as well).

I was documenting my car charging in a notebook for some time, but that is not very useful for relatively fast changes What would be the best way to document the issues?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,673
11,637
San Diego
There is, of course, no way these changes indicate a real energy gain or loss.

Right. The BMS is re-assessing how much energy can be extracted and it is changing rapidly for some reason. Bad reading somehow?

They are the apparent voltage/calibration issues. I have observed these ~10 miles gains before but the charging cable was plugged in overnight and I thought that it was simply some overcharging after charging restarted sometime in the night. I was VERY surprised when I saw the same overnight mileage gains with no cable attached. The temperature changes were near zilch as the car was in garage all the time at about 65F.

The drops near 45-50% SOC happened right after charging was done. Basically, my phone tells me the charging is complete at 145 miles, I go to the car right away (no more than 2 minutes) and see that it is at about 135 miles (and the app confirms that it is at 135 miles now, and % dropped as well).

I was documenting my car charging in a notebook for some time, but that is not very useful for relatively fast changes What would be the best way to document the issues?

If you see it happen in as little as two minutes I would suggest simply taking a video of it happening.

Definitely turn for HVAC etc., of course.

Since you are seeing it go up and down, this seems similar to the case I mentioned. But it seems to be happening much more rapidly in your case.

I’ve definitely seen a couple mile jump on occasion, and even slightly larger than that once or twice, but it has been very uncommon.
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
<<<
If you see it happen in as little as two minutes I would suggest simply taking a video of it happening.
>>>

I'll try. This happens shortly after charging is complete only ... that underscores it is likely some residual charging/discharging in the control circuits or in battery contacts going on.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,789
9,744
Riverside Co. CA
I have seen a few posts here with people reporting small range additions after car sits for a bit, so while there isnt a ton of that, its also not unheard of here.

====================

Putting on the mod hat for a second, I am not going to move this post to the sticky master thread on range loss, because it also discusses a somewhat rarer question about the range fluctuation.
 
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Zoomit

Active Member
Sep 1, 2015
2,197
4,124
SoCal
I have seen a few posts here with people reporting small range additions after car sits for a bit, so while there isnt a ton of that, its also not unheard of here.
I’ll take it a step further and say that all Model 3s do this (and likely Model Y). It started about a year ago with a software update that presumably better reflects the temperature effects on the battery. I noticed it in my TeslaFi data at the time and I’ve seen it ever since. I normally see 1% (3 mi) variations and occasionally more than 3% (10 mi). I think that most people just don’t pay close attention to this or don’t have the data tracking to even see it.

Here’s some TeslaFi data from last week. My car gained 5 miles after arriving at work and 7 miles after returning home.

499D1F48-F18D-48FB-8B0F-4E2F9F8460B8.jpeg
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,673
11,637
San Diego
I’ll take it a step further and say that all Model 3s do this (and likely Model Y). It started about a year ago with a software update that presumably better reflects the temperature effects on the battery. I noticed it in my TeslaFi data at the time and I’ve seen it ever since. I normally see 1% (3 mi) variations and occasionally more than 3% (10 mi). I think that most people just don’t pay close attention to this or don’t have the data tracking to even see it.

Here’s some TeslaFi data from last week. My car gained 5 miles after arriving at work and 7 miles after returning home.

View attachment 610867

Interesting. Totally possible it happens more often that I have observed/paid attention to.

I wonder what is happening here.
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
Here is the result of my last charge today. I charged to 230 miles and immediately disconnected the cable around 3 pm, then after 2 hours, I opened the app and it was 236 miles. You can notice the charge state was higher than the the level I set it to charge before. I wonder if I charge to 100%, will it get my lost range back?
M3 spontaneous range increase.jpg
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
I’ll take it a step further and say that all Model 3s do this (and likely Model Y). It started about a year ago with a software update that presumably better reflects the temperature effects on the battery. I noticed it in my TeslaFi data at the time and I’ve seen it ever since. I normally see 1% (3 mi) variations and occasionally more than 3% (10 mi). I think that most people just don’t pay close attention to this or don’t have the data tracking to even see it.

Very interesting, thank you.
Generally, no temperature effect should result in a noticeable increase of charge unless it is some sort of pyroelectric battery, so this should be some sort of battery voltage fluctuations.
 

BR666T

Member
Dec 19, 2019
99
49
British Columbia
This is happening to my Model 3 LR AWD as well. I will charge to 70% overnight and when I get in the car in the morning I have 73%. I have been talking to one of the mobile techs about this and he says he hasn't heard about.

This started happening right about when the BMS started reporting considerably reduced range - from about 510 km to 475 km. Telsa ran diagnostics on the battery and says everything is fine but they won't provide numbers or any kind of written report.

I suspect it is unbalanced battery cells, but who knows?
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
Interesting. Totally possible it happens more often that I have observed/paid attention to.

I wonder what is happening here.

And I also wonder if this has something to do with the apparent range loss that may be related to some battery circuit charging/discharging issues. A couple month before my car lost range, the battery was under a serious stress when driving 1400+ miles each way on a trip in winter with temperature ranging from 0F to 75F and altitudes changing by 1000s ft. By the way the battery makes popping sounds as hell when going downhill and I thought it is because of rapid recuperation and heating the battery. Am I correct? It is normal?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,673
11,637
San Diego
was under a serious stress when driving 1400+ miles each way on a trip in winter with temperature ranging from 0F to 75F and altitudes changing by 1000s ft. By the way the battery makes popping sounds as hell when going downhill and I thought it is because of rapid recuperation and heating the battery. Am I correct? It is normal?

Yes this is normal. And that does not sound like that stressful situation for the battery. Nice and gloriously cool for it. It’s fine, it’s meant to be used. Using the battery will result in capacity loss. Also age will.
 

Dave EV

Active Member
Jun 23, 2009
1,731
1,193
San Diego
I will charge to 70% overnight and when I get in the car in the morning I have 73%. I have been talking to one of the mobile techs about this and he says he hasn't heard about.
My car has done that for ages. Personally, I'm not worrying about it.

By the way the battery makes popping sounds as hell when going downhill and I thought it is because of rapid recuperation and heating the battery. Am I correct? It is normal?
No, it's from atmospheric pressure changes. It's like your ears popping going up and down hills. I believe there's a TSB where Tesla replaces the breathers in the battery pack with higher flowing units which should eliminate the popping noise.
 

Zoomit

Active Member
Sep 1, 2015
2,197
4,124
SoCal
7.8% is the average loss for 15k miles per the teslafi fleet as another user posted.
I’m not sure what comment you’re replying to here, but the TeslaFi data I see is different.

This shows that the average indicated capacity loss, for Model 3 LR AWD cars, is about 4.5% after 15k mi. [296/310]

C58D84A9-2B04-43A4-957D-DCD8F9464B60.jpeg
 

alexgr

Member
Aug 13, 2019
650
531
Tulsa
I have seen last week the maximum rated capacity as low as 273 miles (12% degradation). In the past two days it is about 285 (9%). One weird thing happened when I parked the car at 66 miles range, got out of the car then back in after 2 minutes and the car was at 60 miles range. And yes, I haven't seen anywhere that a 7.8% degradation at 1 year 15k is average.
 

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