Battery degradation???

[camalaio]

I feel much the same, although I also get a bit nauseated by the coloring book display


This is the key point I try to remember. I'm still unconvinced that the battery needs to calibrated/charged to 100% etc to know rated miles. So far as I know, people have not been bothered by the question enough to provide anything more than anecdotal data heavily seasoned with battery temperature uncertainty.

I share your scepticism. I personally think the BMS is rather spot on for most people and we're just misunderstanding the factors considered in the given numbers. For every report of "I calibrated the battery successfully!", there seem to be 10 more posts where it did absolutely nothing (or like you mentioned, heavily implied to be a temperature-related correction).

And success seems to only be defined as getting it to report more capacity than before? I don't get why everyone assumes a "bad estimate" is always in the direction of reporting less capacity. It could easily report more capacity than exists as well. This could be the case, for example, where some Teslas died before reaching 0% on the display.

everyone I know who bought a Tesla, and that’s probably >100 I’ve talked to or corresponded with over last 8 years, had range as a significant concern... and did their homework. What kind of person buys an entirely new type of vehicle without researching? I think you are describing a very small subset. And, I’ll add, of friends who bought Teslas, the least fanatic who don’t even get on sites like this are also the least worried about range. Maybe the people I know are atypical, but I don’t think so. That’s why Tesla’s customer satisfaction is so high and this forum is so negative. The obsessive will obsess. (Me included I guess) The rest just live happily with their purchase.

I sort of agree. Up until recently, EVs were a more niche crowd, and this crowd wanted to be a lot more researched. More and more people are getting into EVs though without having done all this crazy research, and doing just as much as they do for any ICE vehicle. That means probably no research on the powertrain or how it works. Just gotta plug in instead of refuelling, right? This thought approach might sound infuriating, but it's how a lot of people operate. Just like you can sample a lot of folks that know their mpg or L/100km on their ICE, but plenty of people have no idea. There's nothing wrong with it this process, but it lends a unique challenge to marketing EV range which naturally degrades (amidst a whole list of other factors, like 100-0% being practically unachievable in the first place).

Wasn't Tesla just given a shiny award for one of the worst customer satisfaction ratings too? Maybe it's just because of the disaster of a delivery centre near me, but there's lots of folks upset with the post-purchase experience from Tesla around me.

 

[tomas]

Wasn't Tesla just given a shiny award for one of the worst customer satisfaction ratings too? Maybe it's just because of the disaster of a delivery centre near me, but there's lots of folks upset with the post-purchase experience from Tesla around me.

Tesla received a low quality rating from JD Power related to the ratio of quality complaints to units delivered.

Tesla has consistently received highest customer satisfaction ratings and their market share growth has been off the charts.

I’d say it means that Tesla makes cars so magically enjoyable to drive and so trendy that most owners forgive quality issues and are overall delighted with their cars.

 

[SageBrush]

I’d say it means that Tesla makes cars so magically enjoyable to drive and so trendy that most owners forgive quality issues and are overall delighted with their cars.

i'd say it means that the issues that Teslas have are not viewed by the owners as serious, and/or they are handled in a satisfactory manner.

These report card vendors do a very poor job of weighting the importance of different issues.

 

[smartypnz]

Not sure it has degraded in the 2 2/3 plus years I have owned it. I usually keep it at 90%, but on a recent 5k + trip, I charged full a couple of times and it was 312 each time. Yeah I know it was 320 or so when new, but that was suddenly changed overnight in 2018 with a software update when it went to 312.
The S 100 (different batteries), on the other hand, has lost a bit. It now matches my M3, and it is only just under 2 years (but has 67k miles compared to my 27k)

 

[SageBrush]

Not sure it has degraded in the 2 2/3 plus years I have owned it. I usually keep it at 90%, but on a recent 5k + trip, I charged full a couple of times and it was 312 each time. Yeah I know it was 320 or so when new, but that was suddenly changed overnight in 2018 with a software update when it went to 312.

Same story with my June/2018 Model 3 LR car. At a SOC of 55% my rated miles calculates out to 320 miles at full charge. I don't know how exact 320 miles is but I cannot identify any degradation with confidence. When new the full rated miles was 311, and after a famous update later in 2018 that was supposed to umask the 'true' 324 new car range my car showed 315 miles.

 

[DougWantsALeaf]

Absolutely not. Please don’t spread myths. The cars have a power used per mile constant. This doesn’t change. It doesn’t matter how you drive it. The only factors that play in to it are which model you have and which wheels the car is programmed as having. The cars have an estimated power available in the battery. The range shown is this constant divided by the estimated power available in the battery.

I dont think this is accurate. Some have shown that driving style has impacted their GOM reading.

 

[tomas]

I dont think this is accurate. Some have shown that driving style has impacted their GOM reading.

It is accurate. That is BS mythology. Rated range is a constant.

 

[Candleflame]

I dont think this is accurate. Some have shown that driving style has impacted their GOM reading.

these are very isolated cases and afaik are almost exclusively related to people doing high speed driving or high battery stress driving which presumably from superfast battery discharge and lots of battery heat dissepation causes either early BMS warning of degradation or at least confuses the BMS.

 

[Saturday]

The general consensus I see among this forum is that leaving the car plugged in is best. Is that just because it reduces phantom drain on the battery? Are there other effects?

 

[SageBrush]

I dont think this is accurate. Some have shown that driving style has impacted their GOM reading.

You are confusing the GOM of the LEAF with the rated miles meter of the Tesla.

A GOM is affected by driving style and terrain, etc. In fact that it why it is called a GOM.
This discussion is about a meter that is not a GOM

 

[Candleflame]

The general consensus I see among this forum is that leaving the car plugged in is best. Is that just because it reduces phantom drain on the battery? Are there other effects?

the only real benefit is that you constantly shallow cycle the battery rather than deep cycle the battery. so tesla encourages you to plug it in as often as possible. it may also have some benefit on battery balancing at higher SOC, not sure.

 

[camalaio]

these are very isolated cases and afaik are almost exclusively related to people doing high speed driving or high battery stress driving which presumably from superfast battery discharge and lots of battery heat dissepation causes either early BMS warning of degradation or at least confuses the BMS.

High battery stress would cause real degradation though. If people are seeing reduced reported range after routine high stress, I'd bet good money that's real degradation. Not just a bad estimate.

The general consensus I see among this forum is that leaving the car plugged in is best. Is that just because it reduces phantom drain on the battery? Are there other effects?

It actually increases drain as the car seems to wake itself more often.

The only benefit anyone's been able to tell is it prevents accidental deeper discharges or needing to go somewhere and, shoot, battery is only at 40%. Any battery management that it does, it does when disconnected from charging as well.

 

[SageBrush]

The only benefit anyone's been able to tell is it prevents accidental deeper discharges or needing to go somewhere and, shoot, battery is only at 40%. Any battery management that it does, it does when disconnected from charging as well.

I'l also point out that Tesla never said that keeping the car plugged in when not in use is the way to minimize degradation. They just recommend it as best practice. That is not the same thing, since car ownership encompasses much more than decisions related to battery degradation.

The only thing I think we can take from the Tesla recc is that plugging in when not in use will not lead to substantial degradation. That is a fine thing in and of itself, but people extrapolating this out to mean that it is best practice to avoid degradation are missing a logic link.

The best recc regarding degradation came from Prof Jeff Dahn who suggested battery use between 40% - 70% SoC if I remember correctly (or something very close to that.) People should note that the Prof. was not trying to tell people to use their cars in that manner; he was answering a very specific question of what would constitute an ideal degradation minimization strategy. Tesla on the other hand is recommending a best practice that balances battery degradation with general consumer uses and wants.

Different questions, different answers.

---
I am shooting for long term ownership and my use profile is benign, so I try to adopt best practices as outlined by Prof Dahn as much as practical. I have made three modifications to his reccs:

1. In the winter I charge up to 80%, and I only charge after a drive to reduce battery Li plating
2. In the summer I charge up to 70%
3. I charge when the SoC drops into the 20 - 30% range

Since my car battery shows NO degradation by rated miles after 2+ years I feel pretty confident in saying that I am not doing anything particularly stupid. I suppose I can also add our 7 year old LEAF to my resume, since we handle it along the same lines and I am pretty sure that it stands in the LEAF 99th percentile of low battery degradation in the US despite living most of its life in the mountains and southwest.

 

[Justin27]

This thread is regarding someone's displayed range which is indicative of real battery pack capacity, not driving behaviour or additional usage due to speed/climate/etc. The loss is well-documented on fan forums which are a small subset of owners, and thus not common knowledge for existing or new owners.

Tesla Official Statement on Range

Why is my displayed estimated range decreasing faster than miles driven?
The range displayed is not adapted based on driving pattern or other factors that impact range. When fully charged, the driving range displayed is based on regulating agency certification (Environmental Protection Agency - EPA). To view estimated range based on average consumption, open the Energy app.​

Even if you aren't on the "fan" forums, a 2 second google search will show many topics about this, before AND after you buy the car.

 

[BlindPass]

Even if you aren't on the "fan" forums, a 2 second google search will show many topics about this, before AND after you buy the car.

And why do you think that is?

Hopefully as battery technology and BMS improve, it will be limited to lemons.

 

[DougWantsALeaf]

What I was trying to convey is that there are situations where your max miles on the screen can go down, but not due to degradation. Over time and relatively similar driving style it can be used as a rough measure of battery degradation, but there are other factors which influence that number (driving style, software updates, etc.).

 

[ftmaybe]

I am shooting for long term ownership and my use profile is benign, so I try to adopt best practices as outlined by Prof Dahn as much as practical. I have made three modifications to his reccs:

1. In the winter I charge up to 80%, and I only charge after a drive to reduce battery Li plating
2. In the summer I charge up to 70%
3. I charge when the SoC drops into the 20 - 30% range

Since my car battery shows NO degradation by rated miles after 2+ years I feel pretty confident in saying that I am not doing anything particularly stupid. I suppose I can also add our 7 year old LEAF to my resume, since we handle it along the same lines and I am pretty sure that it stands in the LEAF 99th percentile of low battery degradation in the US despite living most of its life in the mountains and southwest.

My wife's SR+ is a little over six months old and we followed a similar charging regime and she's gone from 250 miles new to 228 now.

I've also read a handful of posts from people here to claim to charge to 90% every time / day and see no reduction in "max range".

It does seem to be a battery lottery or some other factor that we aren't aware of. Really I think there'd be a lot less of these posts from concerned owners if Tesla would just show a "usable Kwh" number. I'm assuming teh car has to know that number if it is using it vs rated miles to get range. Then there would be no speculation about range given outside temperature, use of climate control, hwy vs city, rated vs GOM, etc. Straight up if you showed, say, 51.5kwh when you bought it and now it says 49.3kwh, then you've lost capacity. Simple but I think they don't do that because they want it to be nebulous for marketing purposes.

 

[tomas]

What I was trying to convey is that there are situations where your max miles on the screen can go down, but not due to degradation. Over time and relatively similar driving style it can be used as a rough measure of battery degradation, but there are other factors which influence that number (driving style, software updates, etc.).

This is patently wrong. On a Tesla, driving style does NOT impact rated range. This myth has been propagated by people who do not know the facts, including purportedly some Tesla customer service people - though that could also be how it was heard rather than said. Promoting this is a disservice to owners as it causes unnecessary confusion.

 

[ftmaybe]

I have been running another set of range / wh per mile tests the last two weeks, and I get some conflicting / weird information from the car. For example, the trip meter will claim I used 18kw of power, and the wh/mile vs miles traveled matches that number, but I used 50% of the battery .. so the battery is only 36kw now? and if that's the case, there is certainly no way the car is going to get 228 miles of "rated range". I actually doubt the battery has degraded that much so that makes this usage number even more vexing..


I will say though, I have read here or there a few times about a "$100/kwh" or less industry-ish goal for batteries ...... if the consumer sees that price at any point and you could replace/swap your Model 3 battery for around $5,000, then I don't care about degradation. Even if it drops to 50% capacity in ten years, if I can replace it that cheap, then meh.

 

[SageBrush]

Really I think there'd be a lot less of these posts from concerned owners if Tesla would just show a "usable Kwh" number.

It is trivial to calculate

Take the product of the rated miles remaining and the EPA Wh/mile

Personally I think it is a waste of time since one way or another people will end up calculating the percentage drop in capacity. The drop in rated miles gives the same result. However, the onus is on the owner to use the same SoC and battery temperature in comparisons.