Model S Battery Degradation data

[jerry33]

Is anybody buying model S today, that has a routine HARD REQUIREMENT that the car must achieve very close to its rated range (or actual achieved range), OR ELSE they are stranded on the road?

Not stranded, but having to charge at an inconvenient (aka slow) location. I had one trip where I used the wrong route and added twenty miles. There was also a strong headwind. Ended up with 250 miles traveled and 17 miles rated range left. There were some public chargers I could have used if it appeared that I wasn't going to make it, but I really didn't want to spend an hour to gain an extra 15 miles if I could help it.

 

[roblab]

Just a couple comments.

As I remember, the battery degradation was ALWAYS based on time, not miles or km. Yet every comparison I see here, every graph, is based on distance per charge. Tesla said there would be less than 30% degradation over eight years.

There are some who are shocked that their batteries are degrading, perhaps even normally. That they require that their batteries never degrade or they cannot make it to a necessary destination. As if this is a reason to get Tesla to upgrade the battery or refund in full plus damages.

Really?

And as one has noted, different iterations of firmware have changed the way the car charges and allows usage. We used to have a hidden amount below zero. It seems to have been reduced or eliminated. So do we now have more usable range? Who can even tell?

 

[mlaureti]

I have about 10% lost after 50000km (31250 miles)

Thanks for that.

So, the worst case scenario is approximately a 6% loss of range after about 85,000 km (52,816 miles), which is about a 27 km/17 mile loss. That's also probably with the earlier battery packs (Revision A or B). As new battery pack updates come along with new battery technologies, the range lost over time should be reduced.

Like others said, the software was updated multiple times but I used to get a max charge of 435 km (271 miles) now I get between 386km-390 km (241-243 miles) on a max charge.

I contacted TESLA every time a notice a sudden drop (about 10 km) and they said the software is miss calculating the real capacity of the pack because I rarely do long distances.

Battery type: A

 

[David99]

As I remember, the battery degradation was ALWAYS based on time, not miles or km. Yet every comparison I see here, every graph, is based on distance per charge. Tesla said there would be less than 30% degradation over eight years.

Yes time is a factor, but only one. As research has shown if you keep a Lithium battery at a relatively low state of charge as low temperatures, it will degrade very very little over time. Even years. In other words, time alone isn't an important factor. High temperature and high state of charge over time will degrade the battery much more. Time is a multiplier to other factors.

 

[Maarten ST]

Tesla Model S battery degradation data - with new 100000 km data Tesla Model S battery degradation data | Steinbuch

 

[FlasherZ]

For what it's worth, maybe I have a magic-pack, but my refurb rev "D" pack did a range charge to 266 miles yesterday (268 when newly-refurb'ed), still 90% charges to 240. Car is at 49,500 miles; pack installed at 19,500 in Feb, 2014. 6.2(2.4.160)

 

[loganss]

52,000 miles and my max charge rated range is ~250 miles.

I can't complain. I'm riding this car prob until over 200,000 miles if I can. :biggrin:

 

[CanuckS#69]

78123m, range charge to 396 ideal for me. That's 1.3%, nowhere close to 6% and at 130,000km.

 

[Mario Kadastik]

Well the latest firmware gave my 10km back... When I first got 6.1 I went from 389km to 379km in full charge and now it's back to 389km... About 35000km

 

[islandbayy]

Well the latest firmware gave my 10km back... When I first got 6.1 I went from 389km to 379km in full charge and now it's back to 389km... About 35000km

6.2 initially gave me 1-2 miles, now the latest flavor gave me another 2. I'm at 204 Rated at 18,000 on current referb pack. I havent seen a stable 200+ in a long time now.

 

[PoweredByRain]

With 6.2 I'm seeing a full charge of 416 km rated / 482 km ideal. I've switched to energy mode on the display because I prefer it over a figure which assumes some arbitrary energy consumption per unit distance, so I'm usually only looking at percentages now anyway. It says 100%, so I'm happy. I very rarely charge beyond 90%.

I seem to recall getting 430 km before, but
a) my memory might be off
b) the change might be due to 6.2, it sounds like?

There's 35000 km on the car.

 

[FlasherZ]

For what it's worth, maybe I have a magic-pack, but my refurb rev "D" pack did a range charge to 266 miles yesterday (268 when newly-refurb'ed), still 90% charges to 240. Car is at 49,500 miles; pack installed at 19,500 in Feb, 2014. 6.2(2.4.160)

A range charge last week netted 268 miles (full, original charge). 51,500 miles on the car now. I don't know whether to trust that or not.

I always charge at 80 amps (or 40 if I can't get it). I use range charges pretty liberally (once every 3-4 weeks or so).

 

[electracity]

My interpretation is that the battery pack has hidden capacity that the software "reveals" as the pack ages. Lithium ion batteries deteriorate with time and cycles. The flat trend line simply can't truly reflect cell status.

 

[David99]

My interpretation is that the battery pack has hidden capacity that the software "reveals" as the pack ages. Lithium ion batteries deteriorate with time and cycles. The flat trend line simply can't truly reflect cell status.

Very unlikely that there is any hidden capacity as it would not be available to the driver which defeats the purpose. But even if there was extra to compensate for degradation, it makes no sense to not make use of it until 50k km. Further, what if you max out the extra? Then degradation would look like it's kicking in suddenly again.

There is a much easier explanation. There just isn't enough data available beyond 85k km.

 

[glhs272]

My interpretation is that the battery pack has hidden capacity that the software "reveals" as the pack ages. Lithium ion batteries deteriorate with time and cycles. The flat trend line simply can't truly reflect cell status.

There is no basis for this. The pack voltage is displayed during supercharging. If it were charging to a higher voltage or allowed to run to a lower voltage, this would be revealed. Although it is likely the packs are degrading, the rate of degradation is small. Small enough that it too hard to detect. I have confirmed my pack's range calculation by going from full charge to full depletion in as controlled and measured way as possible. The fact is Tesla has made some fantastically good packs.

 

[Racerx22b]

I have a 2015 Model S85 with just over 3000 miles driven (Feb 2015 delivery). About 500 miles ago my 90% charge ideal range dropped one mile to 239. I was obviously frustrated with losing a mile in just a short amount of time. Lo and behold, it just went back to 240 miles at 90% a week or so ago. I can't explain why. We rarely drop below 150 mile ideal range before charging but over the past few weeks my wife had a few trips down to Miami and back that resulted in charging with less than 100 ideal miles left and for her first trip I did a full range charge just to be safe.

Perhaps that "fixed" it? Who knows?

 

[electracity]

There is no basis for this. The pack voltage is displayed during supercharging. If it were charging to a higher voltage or allowed to run to a lower voltage, this would be revealed. Although it is likely the packs are degrading, the rate of degradation is small. Small enough that it too hard to detect. I have confirmed my pack's range calculation by going from full charge to full depletion in as controlled and measured way as possible. The fact is Tesla has made some fantastically good packs.

Does the DC (supercharger) charge voltage at 90% increase with age? (say under400v to over 400v)

The other possibility is that some battery subpacks are held in reserve at each cycle. Then put back into "play" as the pack ages or needs repair. Tesla obviously manipulates the data if the range is exactly the same each time in a newer car. The estimate should be varying at least +/- 3% if it was derived from pack reading each time.
The extremely rare battery repair issues tells me that they have a reserve with fault tolerance. That an 85kwh pack has more than 85kwh of cells.

There is a much easier explanation. There just isn't enough data available beyond 85k km.

I think the initial trend line is probably THE trend line. And after the initial drop, Tesla puts more capacity into play as needed. After five years or so, they have no more reserve capacity to add.

How to Prolong Lithium-based Batteries - Battery University

 

[glhs272]

Does the DC (supercharger) charge voltage at 90% increase with age? (say under400v to over 400v)

The other possibility is that some battery subpacks are held in reserve at each cycle. Then put back into "play" as the pack ages or needs repair. Tesla obviously manipulates the data if the range is exactly the same each time in a newer car. The estimate should be varying at least +/- 3% if it was derived from pack reading each time.
The extremely rare battery repair issues tells me that they have a reserve with fault tolerance. That an 85kwh pack has more than 85kwh of cells.



I think the initial trend line is probably THE trend line. And after the initial drop, Tesla puts more capacity into play as needed. After five years or so, they have no more reserve capacity to add.

How to Prolong Lithium-based Batteries - Battery University

Several people have taken the Model S battery packs apart. http://www.teslamotorsclub.com/showthread.php/34934-Pics-Info-Inside-the-battery-pack There are no modules or cells held in reserve. What you see is what you get. The modules themselves are identical. The only way to increase the capacity of the battery would be to in essence over charge it or to run it too low. As far as overcharging goes, I have seen no evidence of this. As far as the rated miles shown on the guess o meter is really irrelevant. What matters is the kwh extracted from the pack during a 100% depth of charge cycle, what the voltage is at the top of the cycle and what the voltage is at the bottom of the cycle. As far as seeing how low it can go, I have never tried running it to full dead status (that would be silly). Tesla could allow more of the "brick protection" margin at the bottom of the battery to be used up as the pack ages, but I have seen no real evidence of this yet.

The simplest explanation is probably the correct one. Tesla builds good packs. They are large so they are not typically run at 100% depth or charge. They are heated and cooled to protect from being damaged in that way. The cell chemistries are ideal for the job. The cell electrolyte additives must being doing a good job of protecting the cells. The battery BMS system works well at keeping the cells and modules balanced when charged at >90% (not so much at <90%). Tesla's most innovative and unique technology that they have given to the automotive industry is their battery packs. Clearly where they have spent most of their time and money on is the battery packs. http://insideevs.com/tesla-energy-dates-back-2007/

That said, are they degrading? Yes. Will battery packs fail? Yes. Most of them fail due to faulty contactors (so not really the battery itself, its just that they are located in the battery). But one insidious failure mode of a Tesla pack would be a partial cell failure. If a cell failed (say too much internal resistance) but didn't blow it's fuse. It would eventually bring the whole brick of cells it is connected in parallel to down with it. This would bring the module down. That would in turn bring the whole pack down. This is because the pack is essentially as good as it's weakest cell. It can't charge the pack beyond the highest charge cell and it can't discharge beyond it's lowest cell (hence the whole pack balancing thing). There has been evidence of this failure in at least one car (I can't find the thread on this now). But it is extremely rare. Mostly because Tesla is using very high quality cells, manufactured to very strict tolerances.

 

[Zythryn]

My interpretation is that the battery pack has hidden capacity that the software "reveals" as the pack ages. Lithium ion batteries deteriorate with time and cycles. The flat trend line simply can't truly reflect cell status.

Nothing we have heard, seen or experienced supports that.
There is little data out where the trend line is flat.
Also, lithium batteries tend to loose capacity fairly quickly, then the capacity loss evens out. No, it isn't completely flat, but the capacity loss curve will be less steep.

Also, new cars don't all show the same range. Typically they are close to EPA numbers, but not always exact.

 

[David99]

Remember that the data shown is not battery degradation alone. There are other factors playing in that affect the rated range display.

#1 is cell imbalance. Cells are not 100% identical so they drift apart. Tesla 'fixed' this by putting a lot of cells parallel and combining them into modules. This way Tesla only has to track and deal with imbalances between the modules and not between 7k individual cells. Still it happens and like a chain is only as strong as it's weakest link, the total capacity is reduced if only one module lags behind. If one module is only 0.2 kWh 'behind' the total usable capacity is reduced by 0.2 * the number of modules!

#2 The rated range display is a computer's best guess, not a 100% accurate capacity measurement. Tesla has to be on the safe side. This was explained by an official Tesla email. If you charge your battery only partially (which is good of course) the computer calculation gets less accurate. The longer it happens the less accurate it gets over time. They have improved it with updates but it's never going to be 100% accurate. Since Tesla cannot overestimate, or else people would end up running out of power before it shows zero miles, they are always on the safe side. The display will always show a lower number.

So both these factors play into the data we see and we have no way of knowing which of the three major factors (degradation, imbalance, calculation errors) and at what ration they all contribute to the rated range number. So it's really far fetched to draw conclusions from these numbers and hypothesize about hidden capacity. There is good evidence there is no extra hidden capacity.

- - - Updated - - -

I added my car into the database and I guess a few other people as well since the last screen shot. Now the curve goes up after 85k km.

Another explanation why the curve flattens out is that earlier firmware versions were too pessimistic, again to be on the safe side. Software updates became more accurate and the capacity is calculated a little more accurate and the rate range display doesn't have to be so pessimistic any more. Since these updates came over time while all cars added up miles, it could explain the curve to become flatter as the cars have more miles on them.