If you fast charge, Tesla will permanently throttle charging

[gowthamn]

Tesla should have disclosed this before buying the car. They are withholding information.

 

[SMAlset]

If one is in the market for a 2nd hand 90. Two identical cars turn up, similar mileage and one has throttling (smart enough to ask/check), and the other doesn't. How much more is the non-throttled one worth? Difference might be 5-6 figures, regardless of intended charging protocols? It's to be sold on again, typically...

I get your point and for those that might be expecting to do high mileage driving and need to supercharge regularly, it could be a factor to them depending on their timeframe (business meetings to get to as opposed to recreational traveling). However for the average potential owner out there who does lots of local driving and plans to charge at home, probably wouldn't matter.

Been reading the comments from our European posters and until now never really thought about how much better we have it electrically here in the US for EV use in comparison. Wow home charging taking tens of hours. Yikes.

 

[JRP3]

Yes, Tesla should mention that you might REALLY like their cars because they get a 90%+ approval rating. They should also mention that only occasionally will you find donuts in the service center for the clients. Need I go on?

Make an actual point first.

 

[Cloxxki]

I get your point and for those that might be expecting to do high mileage driving and need to supercharge regularly, it could be a factor to them depending on their timeframe (business meetings to get to as opposed to recreational traveling). However for the average potential owner out there who does lots of local driving and plans to charge at home, probably wouldn't matter.

I agree, but especially is if a free unlimited supercharging car, the next person you sell to might be someone whole makes the off time sensitive road trip.
Now that throttling exists, it's like a service record.

FOR SALE: Throttle Tesla 90kWh. I still get above 85kW sometimes. Great car, served me well. Will accept any offer.

 

[JRP3]

Geez, given Tesla's track record for creativity and innovation, don't you think they are working on or have already fixed this in new battery and BMS design?

Sure, that's possible, but I imagine that there are still outlying use profiles that might cause an issue. A disclaimer would cover such.

I know they somehow fixed what limited my A pack.

You mean your pack can charge above 90kW now? Or was it lower than that and it's now up to 90?

 

[dhanson865]

You own a 60KW, you won't get more than a 96KW charge.

Maybe, and I say maybe that is true for the new 75 software limited to 60KW but as I said in post #80 in this very thread the Model S60 from 2013/2014 charged faster than that.

some can charge at 105 KW (60 KWh with older battery pack, 1.75C charge rate)
some can charge at 111 KW (60 KWh with newer battery pack, 1.85C charge rate)

I've seen posts within the last month or two of Model S 60 owners that still get over 100KW max charge rates. So I'm going to have to disagree with your post. It just doesn't match what other owners are saying.

 

[tomas]

You mean your pack can charge above 90kW now? Or was it lower than that and it's now up to 90?

LOL, no... they "fixed" it in subsequent iterations of battery design.

To your earlier response, I'm just not sure they know all of the outlier cases until they happen. Given a choice of quick to market or imagining and testing every outlier case (such as someone only doing DC fast charging for 2 years), what do you think they should do? Some have postulated that this restriction is a result of the new anode design. Should they have sat on that for 2 years? I don't think this fringe issue is a terrible tradeoff, given the additional power and density that the anode improvement allowed.

 

[SMAlset]

I agree, but especially is if a free unlimited supercharging car, the next person you sell to might be someone whole makes the off time sensitive road trip.
Now that throttling exists, it's like a service record.

FOR SALE: Throttle Tesla 90kWh. I still get above 85kW sometimes. Great car, served me well. Will accept any offer.

I'd still rather buy a used 90D with a good battery and acceptable range that will get me through at least 8 years on the car and spend a few extra minutes at the supercharger. Still won't affect any at home charging at all. For me it honestly wouldn't make a difference.

I suspect this issue was raised at Tesla by reviewing data from cars over time. Sure it was discussed how best to manage the charge rate curve and maybe it's still in the review phase and they are collecting info on the cars in this range. I for one don't believe Tesla did anything nefarious here like I've seen in some comments. Sorry, just don't. I'm sure Tesla will never provide as much info as some here would like to see though. I do get that some are substantially invested in analyzing data and graphs.

 

[TexasEV]

If I knew this then, I might have not purchased the car and wait for next gen battery tech without this problem to buy.

Your user name is No2DinosaurFuel and you might not have bought your Tesla because over time supercharging might take a few minutes longer? You'd rather drive an ICE for a few more years because one day your car might only get 90kW to start rather than 110kW when you supercharge? Talk about a loss of perspective. This thread has really jumped the shark.

 

[Skipdd]

I consider it strange (the first term in your preferred dictionary) and irrational (one of the leading descriptors.)

I'm ok with that phrasing; I don't agree with you, but it's not public branding. You said, "Since no rational person who makes more than half of US minimum wage in his locale would use ChaDemo this way, his behavior is perverse." That struck a nerve. I'm pretty sure you don't care, but alas, I do..

 

[jdw]

Maybe, and I say maybe that is true for the new 75 software limited to 60KW but as I said in post #80 in this very thread the Model S60 from 2013/2014 charged faster than that.

some can charge at 105 KW (60 KWh with older battery pack, 1.75C charge rate)
some can charge at 111 KW (60 KWh with newer battery pack, 1.85C charge rate)

I've seen posts within the last month or two of Model S 60 owners that still get over 100KW max charge rates. So I'm going to have to disagree with your post. It just doesn't match what other owners are saying.

This comparison from 2013 would disagree with that and also highlights the charging curves between an 85 and a 60 kWh battery.

Supercharging Tesla Model S 60 kWh Versus 85 kWh - Video + Graphs

"Interesting is data for power. As it turns out, the 60 kWh version is nowhere close to the 120 kW mark and is falling down fast below 90 kW. Moreover, the 85 kWh version is using full power just for 10 minutes and then drops down too.

Current battery technology is unable to benefit from 120 kW power and the difference to 100 kW is thin. However, in the future better cells or larger battery packs should be able to utilize more power."

 

[ohmman]

That we do not know is not speculation, it is a fact. We do not know.

I never said not knowing is speculation. This kind of statement seems like a purposefully confusing interjection. It's a bit bizarre.

People seem to have motivations to not be too open about it? So that may be affecting what we hear. Thus it is only wise to admit we have hardly been told enough to know with confidence if 5 minutes is the end of the story. It may well be, and I hope it is, but since we don't know how the battery chemistry behaves and analysis works, it is hard to say.

Feel free to explain if you disagree, you know I'll listen and am genuinely interested.

I believe that Tesla should provide us some more detail on this. I've said that from my first post in this thread. I absolutely prefer transparency about this kind of thing, but I also understand how something like this could happen. It's possible someone looked at the trade-off and just implemented it. 5 minutes might have seemed trivial to them. When Tesla comes out and quantifies the cap at 90kW and points out the ~5 minute trade-off, what makes you think that'll change?

For me, the only reason it would change is that Tesla learns that the batteries are degradable beyond the current projections. If that's the case, it's based on something we don't yet know. I don't know how you plan to assign blame or fault, but to me that's an acceptable risk of buying new technology.

One other thing to note. There's a trade-off here, right? Battery degradation (some unspecified amount) vs. faster charging. Some have said they'd prioritize faster charging over battery degradation, but that seems terribly short sighted to me. The former is going to cannibalize the latter anyway. If you charge quickly at the cost of battery life, your battery life will eventually make it so you are permanently charging more slowly due to reduced range. So in a way it's lose/win vs. lose/lose.

 

[stopcrazypp]

Actually in the early days many of us assumed that faster charging would be harder on the cells and speed degradation. That's what I always told people, until the work by Prof Jeff Dahn seemed to show otherwise, as did the long term pack capacity studies. Faster charging does not seem to negatively impact capacity though it does seem to impact peak charge rates in some cases.

I should caution saying general statements like this. The factors that go into this is very complex and I doubt Tesla wants to attempt to educate all users about the nuances of that (and the general public won't bother to learn the nuances, more likely they latch on a certain point and generalize).

For example faster charging = better (or worse), can't be generally applied. As you pointed out above somewhere, the professor pointed to fast charging suppressing some negative side effects. However, how low and how high? Linked below is a transcript for this talk.
Why do lithium-ion batteries die? (long)

There are a bunch of competing factors (linked presentation goes into details). Just to discuss some briefly (or as briefly as possible).
http://www.nrel.gov/docs/fy14osti/62813.pdf

Let's first square away the factors that largely point to rapid charging as negative:
Low Temperature: Lithium plating can occur, so Tesla's BMS refuses to charge until it brings battery temps up. Rapid charging in low temperatures are even worse.
Change in temperature: Rapid charging is more likely to lead to larger thermal swings that causes stress.
C-rate: High C-rate charging can lead to lithium plating. It also causes fractures in the active material. This is where the idea of faster charging being worse generally comes from.

Now for factors that require a balance:
High Temperature: We know higher temperatures are worse for degradation because it accelerates the chemical processes. Naturally we expect faster charging = higher temperatures. However, this neglects one critical factor: time. A rapid charged battery may see higher peak temperatures, but it sees it for a relatively short amount of time. A battery charged at level 2 AC (or worse: level 1) sees higher than ambient temperatures for a much longer amount of time. So there's a balance between the two. There is some optimal point (which may also change depending on ambient temperatures). For example, could be possible 90kW is the optimal point at room temperature for a given kWh pack, so charging both slower or faster than that is worse.

DOD/SOC window: People using rapid charging tend to using a larger DOD window, which is worse for the battery. However, they also tend to start from a lower SOC, so might have a lower average lifetime SOC (which helps battery life). Again this is a balance.

Calendar vs cycling: Calendar and cycle degradation are not additive. Cycling suppresses calendar based electrolyte film growth, but increases SEI growth. Professor Dahn talked about how this can lead to rapid charging actually being better than slow charging because it reduces the amount of time for these reactions to occur. This can cause a second knee in the curve (along with temperature factors.) This can lead to a situation where for example 40kW and 90kW are best at room temperature for a given kWh pack and anything slower, faster, or in between is worse.
https://www.nrel.gov/transportation/assets/pdfs/45048.pdf

Side points:
Architecture based effects: Tesla's BMS/thermal control/infotainment system has a significant amount of overhead consumption. That is why 110V charging is actually less efficient than 220V charging. For similar reasons, 220V charging may also be better for the pack than 110V charging.
AC vs DC charging: many people said there should be no difference between AC and DC charging, since the battery sees DC in both cases. This is not true, AC charging uses an onboard charger which generates heat that the car's cooling system has to remove (and in some cars the charger is near the pack, so heat can migrate). DC charging uses an offboard charger, so the car only has to deal with charging heat, not the AC/DC conversion heat.

Now how can Tesla explain all of this to a general user and in a way that they can apply practically? Note, they can't just say a certain kW is optimal, because this may vary depending on temperature, chemistry, capacity (the battery cells care about C-rate, not the kW), architecture (example: 100kWh uses different cooling/cell packing). And as above, there may be two (or even more knees) in the curve.

I should also note, even they may not be sure of all the mechanisms going into this (esp. for different chemistries). A lot of the battery degradation models are still under research (there are multiple different types).

 

[tomas]

There's a lot of strong-principled (but IMO slightly naive) talk going on in this thread. I'm going to say a few things that I think Tesla cannot say, but I suspect they are thinking.

1) I'm guessing Tesla is learning some of these things as they analyze date from long term use. Tesla has introduced the first long range, significant production volume BEV. There was a lot of learning from the Roadster that went into the S/X generation, but there have been a LOT of battery and BMS innovations since the Roadster. Should they hold each one of those until they can test 5 year fringe use cases? Is it possible that they might miss a use case? Their very survival from day one has depended upon speed to market, which they have to balance against getting everything 100% buttoned down. And, in many dimensions of the design, they are pioneering... vs other car companies who are simply further perfecting a century-old design concept. Personally, I do not think they are putting stuff out without full disclosure as much as they are putting stuff out after a reasonable amount of testing, and then learning from fleet data.

2) The #1 fears of BEV buyers? Batteries. Range and battery degradation, to be specific. To sell meaningful volumes of cars, Tesla has had to directly address those fears. With Superchargers. With a complex BMS. And with a constant effort in iterations of the battery technology, the supercharger network, and the UI to DE-EMPHASIZE range concern and to reassure regarding degradation. SO, even though the "enthusiasts" on this forum would LOVE to have full disclosure of every line of code in every release of the BMS... it would be completely counter to Tesla's marketing imperative (making BEV objections disappear) to feature all of the caveats we want on their website or in their marketing.

3) Has anyone here ever worked with a corporate legal department? C'mon! You cannot just go out and say "hey, we discovered this so we did that, and here's how it affects your car". That is inviting liability. You just have to address issues as you find them, issue finely worded statements when you have to, hope concerned customers or advocates will get some perspective, and fight actions if they occur. Technology people hate this (and I'm positive this forum is heavily populated with them), but it is reality.

4) Gosh, I wish the internet had been around when Henry Ford came up with the automobile assembly line. Do you think they found and fixed a few things as they went along with the Model T? I'll bet they did.

Personally, what I look for in Tesla's behavior is a bit different than some others here. Many forum members get super-anguished and offended that Tesla seems to repeat the "error" of not communicating limitations or design tradeoffs. I actually see that as a good thing... it means they are continuing to be ambitious and push the envelope... which they absolutely need to do in order to succeed. What I also look to is whether they analyze data, listen to feedback, and cycle the lessons learned back into product design. From my experience, it seems that they do. Maybe not fast enough to please all of us, but we ARE a tough crowd, aren't we?

 

[Archer]

So the bottom line is for those who DC fast charge almost exclusively, you eventually won't have the ability to charge an additional 20KW worth of energy for about 5 mins and only when plugging in to an unpaired stall with a low SOC and outside temperature is nominal. So this translates to not getting an additional 5 miles as quickly as others who are unaffected in exactly the same situational. Is this really worth the anger?

What if Tesla never allowed everyone to charge over 90KW from the beginning and stated that it's for the longevity of the battery. Would there be the same outrage?

FWIW, I have 130K miles on my 2014 P85. For the first 100K miles, 80% were supercharged, the rest was from my HPWC. The last 30K miles has been the exact opposite. At a recent supercharge, I got 112KW for about 5 mins and it tapered as expected. So 86K miles on my car were from SC and I haven't experienced any throttling yet. If it does happen, I would still love the car and recommend it.

 

[SageBrush]

I'm ok with that phrasing; I don't agree with you, but it's not public branding. You said, "Since no rational person who makes more than half of US minimum wage in his locale would use ChaDemo this way, his behavior is perverse." That struck a nerve. I'm pretty sure you don't care, but alas, I do..

You are sure I don't care about what ?

I was pointing out that his ChaDemo behaviour saves him about $4 an hour, or about one half of the current minimum wage. If he can find a McDonald's that lets him plug-in and fry some food, he can more than double his charging savings.

 

[JRP3]

Now how can Tesla explain all of this to a general user and in a way that they can apply practically?

By including frequent high power charging in their existing list of things that may degrade the pack instead of explicitly stating that it won't.

 

[JRP3]

To your earlier response, I'm just not sure they know all of the outlier cases until they happen. Given a choice of quick to market or imagining and testing every outlier case (such as someone only doing DC fast charging for 2 years), what do you think they should do?

I'm quite sure a new anode design will have been extensively stress tested before going into any vehicle, at even higher C rates than SC's produce. You don't come up with a new chemistry and toss it into a vehicle after a few months. Panasonic has been testing the chemistry for years. The expected behavior of a lithium cell is accelerated degradation at higher C rates so the default position should have taken that into account.

 

[McRat]

On another site, a Tesla owner commented he would enjoy more time at the chargers, it's relaxing. He was not being sarcastic.

So is it actually even an issue?

 

[stopcrazypp]

By including frequent high power charging in their existing list of things that may degrade the pack instead of explicitly stating that it won't.

But the key thing is, ironically, it appears they are using the BMS to ensure that high power charging will not degrade the Tesla pack excessively. This may mean a limit on the max high power charging rate, but they are still allowing high power charging.