25% slower Supercharging due to degradation

[David99]

Triggered by the discussion about how Tesla reduces your charge rate when you charge on DC a lot If you fast charge, Tesla will permanently throttle charging I wanted to find out if and how much slower my car charges compared to when it was new. My car is 3.7 years old and has 133k miles on it. It's a 2014 85.

While I never noticed a sudden decrease and also not a cap in the highest charge rate, I did notice it takes longer to charge at Superchargers. Now there are a lot of factors that can influence charge speed at a Supercharger. So I captured the data from many Supercharging sessions and noted other factors so I would be able to compare.

It turns out that my car now charges 25% slower than when it was new. 25% is a significant difference. Big enough to make a real world difference. Here are two typical charge curves when the car was new and as it is now.


Both times it charged from 16% battery to 92%.

Looking at my road trips, on average I need to charge about 40 kWh at each Supercharger to make it to the next one. Looking at the time it takes to charge 40 kWh makes the difference more clear. When the car was new, it took about 27 min, now it takes about 35 minutes. That's a difference of 8 min per charging stop. That's significant enough not to be ignored. There are two factors that play into this. First, Tesla is clearly reducing the charge rate as the battery gets older. The graph shows that clearly.

The other factor is capacity loss due to degradation. When my car was new it had 270 miles range, now it has 246. In other words to charge 200 miles, I had to charge to 74% when the car was new, now I have to charge to 81%. Obviously, this takes longer even if the charge rate was the same. So both the reduction of the charge rate (faster taper) and the fact that we have to charge to a higher percentage both add time.

Concrete example is our annual road trip from Los Angeles to Minneapolis. There are about 15 Supercharger stops. It adds up to 2 hours extra time, one way. I'm honestly not too happy about it. I don't care having lost 25 miles range. I never drive more than 150 miles in a day. But having to wait 8 minutes longer at every Supercharger is something that affects me a lot since I do a lot of road trips with my car. About 80 k miles out of the 133 I have on my car are just roadtrips.

I also made a quick video about it.

 

[Missile Toad]

3.7 years ago, the Superchargers had an average age of (probably ) 6 months. Today, even accounting for some locations that have undergone expansion, I would guesstimate that the age of a typical Supercharger cable (and equipment in the 'corral') is 18-24 months. Is it possible, that the older Superchargers contribute with 'soft failures' in individual 10A modules in their 'stack' or fraying internally to the cable? In other words, how much of the degradation you note, might be an artifact of a changing charging environment?

As a data point, I note that I can call the Tesla Roadside support, and ask them, before rolling up to a SuperCharger, which of the stalls has the better service. They will actually state, with authority, try stalls "1A, and 5B", or something like that. So, that certainly implies that not all stalls are created equal, and by extension, not all sites will operate identically. Best way to test this theory might be to run over to a new SuperCharger site and try your 16-92% charging over there to see how it goes?

 

[Electric700]

David99, I'm curious to know whether you've balanced your battery (by charging to 100% and leaving it for about a half hour)? Some people here do that once a year, though your car should automatically be doing it.

Also, have you talked to Tesla about your charging rate or contacted [email protected]?

 

[David99]

David99, I'm curious to know whether you've balanced your battery (by charging to 100% and leaving it for about a half hour)? Some people here do that once a year, though your car should automatically be doing it.

Also, have you talked to Tesla about your charging rate or contacted [email protected]?

Balancing is something the car does on it's own perfectly well. My cells are as good in balance as it gets. I've been monitoring the cell voltages for over a year and they are usually within 0.1%. That's as good as it gets.

I have asked Tesla several times about slower than normal Supercharger rates. Their response was always that the rate can vary depending on many factors so what I'm seeing is within the normal variations.

 

[Galve2000]

In my opinion, reduced SuperCharger speed is not due to your aging Model S battery. I believe it has to do with Tesla changing the taper of the superchargers (most likely for the benefit of battery longevity).

The following is coming from me, not Tesla, so make of it what you will.. but it turns out that pumping 115 kW into the battery for more than a few minutes is probably very stressful on the battery. so Tesla decided we would all hit 119 kW shortly after we 1st plugged in, but after 3-4 minutes (no joke) our charge rate would be back down to 90 kW and keep on dropping from there. (sucks)

my car was built in May 2015 (one of the last to ship without LTE support if you must know) and delivered to me in June 2015. I have just under 25,000 miles on my 85 kW battery and still get 242 and 243 rated miles of range at 90%. I consider my vehicle moderately used at best. (The poor thing has spent a lot of time "in the shop" and I travel a lot by air while my car otherwise sits home collecting dust... should I sign up for Turo? its not easy to do in NYC.)

Anyway, my miles are pretty low for the age of my car.

my SuperCharging speeds are noticeably slower than they were during the 1st 15,000 miles. its not the age of the car. It't Tesla playing with the SuperCharging speed.

Concrete example is our annual road trip from Los Angeles to Minneapolis. There are about 15 Supercharger stops. It adds up to 2 hours extra time, one way. I'm honestly not too happy about it. I don't care having lost 25 miles range. I never drive more than 150 miles in a day. But having to wait 8 minutes longer at every Supercharger is something that affects me a lot since I do a lot of road trips with my car. About 80 k miles out of the 133 I have on my car are just roadtrips.

I haven't gone on a super long road trip to see the effects of this new supercharger throttle. but TeslaFi confirms that my average SuperCharging speed is in the "mid-70's" KW and I am nearly certain that my average SCing speed averaged in the "high 80's" for the 1st 15,000 miles. so it will definitely make driving from NY to FL (and back) a longer proposition.

I don't know if/when I will undertake this again so it may be a moot point -- but it still stings a bit to know that SuperCharging is now slightly less "super" -- and the OP experience, quoted above, really scares me.

 

[David99]

... Best way to test this theory might be to run over to a new SuperCharger site and try your 16-92% charging over there to see how it goes?

I have Supercharged about 600 times so I'm well aware of variations. To make sure that it's not just different superchargers or old equipment or any other factor I waited many months and collected data from many different Supercharging sessions before I put this post and video together. There sure are many variations that affect speed. The curve that is labled old is actually a 'good' Supercharge session. Often I get an even lower rate due to other issues. The dreaded drop to 60 kW, stall sharing, extreme temperatures, bad Supercharge stalls and so on. I'm experiencing all of those and that's all fine (more or less). For this post and conclusion I made sure I eliminated all other factors.

 

[hacer]

... When the car was new, it took about 27 min, now it takes about 35 minutes. That's a difference of 8 min per charging stop. That's significant enough not to be ignored.
...
Concrete example is our annual road trip from Los Angeles to Minneapolis. There are about 15 Supercharger stops. It adds up to 2 hours extra time, one way. I'm honestly not too happy about it. I don't care having lost 25 miles range. I never drive more than 150 miles in a day. But having to wait 8 minutes longer at every Supercharger is something that affects me a lot since I do a lot of road trips with my car. About 80 k miles out of the 133 I have on my car are just roadtrips.

Why would you care at all about 8 extra minutes of supercharging if you're making a road trip, but will not go further than 150 miles in a day? That is 1 supercharger stop a day, and you're taking like 13 days to drive to Minneapolis. So maybe almost 3 hours of driving, 35 + 8 minutes of charging and you call it a day. How does that extra 8 minutes matter when you're going to lounge around at intermediate stops for pretty much the whole day?

 

[gaswalla]

I don't understand why folks are so dismissive of OP. With that approach, we'll never get to the truth. OP definitely has slower supercharging... the question is why. Dismissing his two data sets does not solve the riddle.
It would be great to have more data points between new and 133k miles. Also, there was a mention about superchargers aging - truth is that there are a lot of new superchargers also - maybe data points from a new supercharger vs an older supercharger. Another thing: ambient temperature may have an effect (more specifically: temperature of SC equipment as well as battery temp).
Let's look into figuring out what's going on here.
Anyone have a loaner battery and can compare charge times with the loaner vs original?

 

[EinSV]

I have Supercharged about 600 times so I'm well aware of variations. To make sure that it's not just different superchargers or old equipment or any other factor I waited many months and collected data from many different Supercharging sessions before I put this post and video together. There sure are many variations that affect speed. The curve that is labled old is actually a 'good' Supercharge session. Often I get an even lower rate due to other issues. The dreaded drop to 60 kW, stall sharing, extreme temperatures, bad Supercharge stalls and so on. I'm experiencing all of those and that's all fine (more or less). For this post and conclusion I made sure I eliminated all other factors.

About 600 Supercharges is a huge number — especially in less than 4 Years — something like once every other day.

Is that is your primary/regular charging method?

 

[TaoJones]

It’s my primary charging method, plus I drive a lot.

My rule of thumb for a “good” rate, average, is 1%/minute. So I’m at an SC for an hour and 15 minutes anyway more often than not, since I try to live between 15% and 90%. I don’t have a problem arriving at an SC with 2%, but it’s not really necessary most of the time, I do NOT want to see the “drive at 45/55/65 to reach your destination” messages, and pushing it isn’t always a best practice.

The extra time at SCs while on the road is annoying - amplified during this year’s travels by an unprecedented number of bad pedestals and towers.

This will of course undoubtedly get worse before it gets better.

It’s an adventure .

 

[roblab]

This will of course undoubtedly get worse before it gets better.

It’s an adventure .

Imagine how bad it would be if you'd bought a Toyota or Nissan.

 

[Missile Toad]

I think this whole line of inquiry is very helpful. At the end of the day, Tesla controls a) the battery production lines; b) the software updates and c) the supercharger install and maintenance. It is up to Tesla to make them all play together well to achieve a balance between battery longevity decay and daily Supercharger taper. New buyers should have some baseline expectations for both longevity and for session tapers during every phase of car ownership. For better or worse, we are all beta testing this frontier..., and it would behoove Tesla to achieve greater transparency. I think OP has given a good overview of what happens over 100K miles on what seems to be a first generation of the battery (incidentally, which battery pack do you have 'a'; 'b'; 'c' or something else?).

 

[Lanber]

What method of controlling power does Tesla use while supercharging? This is me speculating.

The car asks for Amps from supercharger, the voltage rises and at any given SOC the car will only accept so and so much voltage. So it reduces amps accordingly.

As batteries get old it takes less amps to reach the threshold volt due to aging. Ofcourse Tesla can also have edited the charge curve.
Your 2014 S85 seems to be a lot further down the line in terms of supercharging speed compared to my 2013 S85. But I also see reduced speed in the form of car starting tapering sooner, at 22% now and then being below the original curve all the way up but less so as charge level goes high.

 

[David99]

Why would you care at all about 8 extra minutes of supercharging if you're making a road trip, but will not go further than 150 miles in a day? That is 1 supercharger stop a day, and you're taking like 13 days to drive to Minneapolis. So maybe almost 3 hours of driving, 35 + 8 minutes of charging and you call it a day. How does that extra 8 minutes matter when you're going to lounge around at intermediate stops for pretty much the whole day?

When I'm on road trips of course I drive more than 150 miles a day. On typical road trips I drive 600 to 1000 miles a day. 25% longer charge time is significant.

 

[David99]

About 600 Supercharges is a huge number — especially in less than 4 Years — something like once every other day.
Is that is your primary/regular charging method?

My primary charge method is at home over night. But as I said, I do take a lot of road trips and about 80k miles out of the 133k miles I have on my car are road trips and that's where I Supercharge of course. 80k miles divided by 120 miles (that's the average I charge at a Supercharger) comes out to something like 650 charge sessions.

 

[MP3Mike]

You must have an interesting definition of never.

I never drive more than 150 miles in a day.

When I'm on road trips of course I drive more than 150 miles a day. On typical road trips I drive 600 to 1000 miles a day.

 

[David99]

I don't understand why folks are so dismissive of OP. With that approach, we'll never get to the truth. OP definitely has slower supercharging... the question is why. Dismissing his two data sets does not solve the riddle.
It would be great to have more data points between new and 133k miles. Also, there was a mention about superchargers aging - truth is that there are a lot of new superchargers also - maybe data points from a new supercharger vs an older supercharger. Another thing: ambient temperature may have an effect (more specifically: temperature of SC equipment as well as battery temp).
Let's look into figuring out what's going on here.
Anyone have a loaner battery and can compare charge times with the loaner vs original?

Thanks a lot.

I think I mentioned it before. I logged Supercharging sessions for many years. I also have access to the CAN bus data from the car so I can see what is going on. I did not just take one Supercharing session recently and used that as my data point. I charged at many different Superchargers in various conditions, different age of the Superchargers and so on trying to eliminate any other factors. No matter where, what the ambient or battery temperature is, no matter if the Supercharger is new or old, I cannot get a charge rate higher than what is in my graph marked as 'old'. That's as good as it gets no matter what. It is not high temps, old superchargers, bad stalls, paired stalls. I'm very well aware of all the other factors and I see these factors sometimes slow down the Supercharger. For this comparison I made sure that I used a data set that is as good as it gets with my car at this point.

 

[David99]

You must have an interesting definition of never.

I should have said 'almost never'. My bad.

 

[hacer]

When I'm on road trips of course I drive more than 150 miles a day. On typical road trips I drive 600 to 1000 miles a day. 25% longer charge time is significant.

Well in that case you probably benefit from the extra time spent charging. 1000 miles in a day results in an extreme length of time in a seated position which is not good for your health. Even if you could average 75 MPH, which is doubtful, the driving time alone is 13:20. Even a 600 mile day (at a more realistic average speed of 65 MPH) would have you seated for 9:14 so having forced longer breaks is still a health benefit if you walk around or at least stand upright.
My experience has been that more superchargers have been constructed directly along highways which allows for faster travel than before despite slower charging because I no longer have to go as far out-of-the-way to charge, saving both time and miles. I myself am grateful for the charging breaks where I walk around while the car charges on long trips.

 

[bluetinc]

David,
I've seen my share of Supercharger slowing also, but I haven't spent the time to track it to the level you have. Thanks for sharing all the data.
I've found that I rarely see a "quality" Supercharge for those "other" reasons, especially Superchargers that have failing chargers in the stack that seem to overhead and ramp down very quickly. It will go from 115kW to 70kW in just a couple of minutes. It's been very hard to tell when it's a problem with the car or the chargers, except when I swap spots (on the spot when I'm there to see it), and the rates go right back to where they should be.
I did also find one thing wrong with my car, which has seemed to make a difference, which is that my louvers had failed, which decreased the cars ability to cool the battery during charging. Since then, my rates (after I find the good charging spot) seem much closer to normal.

Well in that case you probably benefit from the extra time spent charging. snip...

Out of curiosity, when do you feel that "extra" delay when charging goes from a benefit to a issue? 5 minutes, 10, 30, and hour?

-Peter