[WopOnTour]

Recent update on a thread that was making the rounds in 2015

Take if for what it is I guess

https://steinbuch.wordpress.com/2015/01/24/tesla-model-s-battery-degradation-data/

WOT

 

[kns]

Several of the most recent comments in Steinbuch's thread express disagreement with the data, the charts and the conclusions. Most interesting to me was this paragraph, extracted from one of those recent comments.

"Every part of this data and conclusions relies on a single completely unreliable assumption: That the displayed range by your cars instrumentation is accurate, or nearly accurate. If it is not accurate, every conclusion about battery degradation is wrong. The stated range from your car may be very far from true. Mine surely is. My 2016 90D continues to show a 100% range of about 270 miles. Yet my battery has degraded to hold only 70-73 kWh. And my best attainable range is about 200 miles. A service center rep pulled the vehicle logs and told me that my car and battery are performing normally."

Elsewhere in the thread it is stated that the battery warranty is not applicable to normal degradation, only to excessive degradation. Ouch. I am very happy to own a GM EREV instead of a Tesla BEV.

EDIT: The cells in the TM3 will use a different chemistry but this data could give potential buyers food for thought.

KNS

 

[edk-austin]

As the writer points out himself, there is not enough data to substantiate the downward end of life cliff on the higher mile cars. So it would seem irresponsible to show that order of polynomial curve fit on the first chart. We all agree that batteries will wear out eventually, but if it is 160K miles or 500K miles, will be very different across vehicle type and charge/discharge profiles.

It will be interesting to see how this data creates battery recycling biz cases. We DO want lithium recycling/re-use to succeed. Will it take lithium PCR (post consumer recycling) regulations to make it happen?

Thanks for the link!

 

[DonC]

This is actually better on the short end than what Panasonic has published. The Panasonic official stats show faster degradation early and then a flattening curve. Not sure why you wouldn't just use these numbers, which means the sudden drop is very likely not going to happen.

On the other hand, all batteries degrade with time and use. So unless you can put the car in a freezer none of this should be surprising.

 

[scottf200]

Data point. On TMC forum there are threads for people to post their 90% numbers so I had numbers there.

Mar 3rd 2016 is when I got my P90D X. Supercharged to 90% showed 224 mi (224/9*10=248.88 @ ~100%). The P90D is rated for 250.

Mar 24th 2017: My P90D is at 28.3K miles and at just over 1 yr I am at 213.3 Miles @ 90% (213.3/9*10=236.6 @ ~100%)

So 213.3/224 = 95.2% -- This is what I expected based on all the Model S history and various charts. Earlier loss then level off. Hoping to upgrade to a larger battery in several years for more detoured drives and rural America. i.e. picking up my son from college is 100 miles each way from a supercharger. Not ideal at winter break w/less range avail

Obviously I use Superchargers a fair amount. I mainly use them to charge just enough plus 10-15% buffer to get to the next one (i.e. what car's trip planner suggest). I occasionally use them to charge to 98-100% for some special cases/destinations. I leave the house with 100% on the first days travel and use an Android app to get it to that point fairly close to when I'm leaving. I originally charges to 90% daily but in last 6 months only do 80% daily.

Aside: I am currently over 29K and will be traveling back to SD for Tesla car meetup in May then on to MT.

Volts: We still have our 2011 Volt but my college son drives it when he gets home. My wife's 2016 Volt gets < 500 miles per month on it.

 

[Michaelh310]

Several of the most recent comments in Steinbuch's thread express disagreement with the data, the charts and the conclusions. Most interesting to me was this paragraph, extracted from one of those recent comments.

"Every part of this data and conclusions relies on a single completely unreliable assumption: That the displayed range by your cars instrumentation is accurate, or nearly accurate. If it is not accurate, every conclusion about battery degradation is wrong. The stated range from your car may be very far from true. Mine surely is. My 2016 90D continues to show a 100% range of about 270 miles. Yet my battery has degraded to hold only 70-73 kWh. And my best attainable range is about 200 miles. A service center rep pulled the vehicle logs and told me that my car and battery are performing normally."



KNS

This is the key point. Tesla fan-boys look at the rated range display and treat it as truth. I cannot find...can anyone point me to it...information on what this "rated range" means?

I understand it applies some reference miles/kWh to the battery's estimated capacity. Don't tell me that...tell me how the instrumentation reaches its estimate of the battery's remaining capacity? Model? Measurement? What?

Furthermore, there is the possibility (unless someone knows one way or the other??) that the BMS widens the depth of discharge window as the battery ages, thus masking genuine battery capacity fade.

I think there is a distinct possibility the fan-bays are drinking Elon's Kool Aid.

 

[scottf200]

Furthermore, there is the possibility (unless someone knows one way or the other??) that the BMS widens the depth of discharge window as the battery ages, thus masking genuine battery capacity fade.

My 2011 Volt was showing the same max range during the summer after 3 years and 45K miles. Hmm...

This is the key point. Tesla fan-boys look at the rated range display and treat it as truth. I cannot find...can anyone point me to it...information on what this "rated range" means?

I understand it applies some reference miles/kWh to the battery's estimated capacity. Don't tell me that...tell me how the instrumentation reaches its estimate of the battery's remaining capacity? Model? Measurement? What?

Projected range is more useful for real traveling or long days around the city/suburbs, IMO:
There is a projected range based on weather, elevation, current driving (Wh/mi), etc. There are displays in the car that show you this which I will include below. The Tesla built-in Trip Planner maps out trips longer than your battery range. My longest trip was from IL to MT. It creates supercharger waypoints, tells you how long to charge at each of the waypoint with a ~15% buffer (i.e. 35ish miles on my P90D). So when you stop at these waypoints and eat/snack/bathroom/stretch breaks, the phone app (or car if in it) will tell you when you have enough to continue. If you are traveling and it projects you may not make it based on headwinds, driving speeds, etc different than your past X miles, then it may tell you to slow down to XX MPH to make it.

Nice highlevel TMC post by a moderator several years ago.

Doug_G, Jan 5, 2013
Ideal - how far the car will go if driven at a steady 55 mph on level ground at moderate temperatures.

Rated - how far the EPA says the car will go given their tests. Equals 88% of Ideal. Just a slightly more conservative version of Ideal.

Projected - how far the car calculates you will go if you keep consuming power at the rate you are currently. The distance it is calculated over can be adjusted by changing the graph settings. This is useful on long trips when you are driving in a consistent fashion (e.g. highway). If Projected is greater than the distance remaining on the GPS, then you are going to make it to your destination. If not, either slow down or stop and charge!

Both Ideal and Rated give an indication of how much power remains in your battery. Projected depends on how you've been driving, weather, heater use, etc.

Note: These screens are a little old but the most current ones are very close.

 

[Raymondjram]

Although all this may fly over many drivers' head, they need not know the details. All they really need is what is the manufacturer's warranty details are, how to get warranty service if their EV battery does lose capacity, and how to reduce the degradation so the battery will maintain its capacity for a longer period than average. Many Chevy Volt owners know that its battery has a reserve to aviod seeing a loss, and that the Volt's software was coded to prevent using that reserve, so the total capacity shown to its owner is constant and simple to manage. I don't know how the new Chevy Bolt EV software do the same, but the GM approach is better for those same drivers who prefer to have a reserve than those who want to run the full batteyr capacity.

What these battery manufacturers should provide is their results from comparing full charge/discharge cycles (for long range driving and Supercharge uses) to occasional and nightly charges at lower rates. I prefer to do the latter, since my trips are short, and I can charge overnight at a present 7.2 kW rate (29 miles an hour) or at possible higher rates (up to 16 kW or 64 miles an hour) with my present EVSE 9see my signature).

 

[Michaelh310]

So do we have an answer to the question: How does the Tesla onboard computer reach its estimate of the battery's total usable capacity?

The only positive test I know is to run the battery from top to bottom (however those are defined in that particular car) and measure how much energy is delivered. That's what Idaho National Labs does. Anything else is, as best I can see, an estimate.

And although INL hasn't tested long term battery fade in a Tesla, they have done so in a Mercedes which has a Tesla drivetrain and power system. The Mercedes shows fade in line with every other car they have tested, no magic was apparent.

In answer to the post above, unlike the Gen 1 Volt which used only a small portion of the DOD window, the Bolt uses almost all the capacity if fully charged and discharged. So they do not have the option to increase the window.

 

[Bluesideup]

Several of the most recent comments in Steinbuch's thread express disagreement with the data, the charts and the conclusions. Most interesting to me was this paragraph, extracted from one of those recent comments.

"Every part of this data and conclusions relies on a single completely unreliable assumption: That the displayed range by your cars instrumentation is accurate, or nearly accurate. If it is not accurate, every conclusion about battery degradation is wrong. The stated range from your car may be very far from true. Mine surely is. My 2016 90D continues to show a 100% range of about 270 miles. Yet my battery has degraded to hold only 70-73 kWh. And my best attainable range is about 200 miles. A service center rep pulled the vehicle logs and told me that my car and battery are performing normally."

Elsewhere in the thread it is stated that the battery warranty is not applicable to normal degradation, only to excessive degradation. Ouch. I am very happy to own a GM EREV instead of a Tesla BEV.

EDIT: The cells in the TM3 will use a different chemistry but this data could give potential buyers food for thought.

KNS

It was my understanding that GM didn't cover normal degradation either. Are you stating that when the Bolt doesn't match the same range when it was bought that GM will somehow cover the loss of miles and give you a new battery?

 

[Bluesideup]

This is the key point. Tesla fan-boys look at the rated range display and treat it as truth. I cannot find...can anyone point me to it...information on what this "rated range" means?

I understand it applies some reference miles/kWh to the battery's estimated capacity. Don't tell me that...tell me how the instrumentation reaches its estimate of the battery's remaining capacity? Model? Measurement? What?

Furthermore, there is the possibility (unless someone knows one way or the other??) that the BMS widens the depth of discharge window as the battery ages, thus masking genuine battery capacity fade.

I think there is a distinct possibility the fan-bays are drinking Elon's Kool Aid.

I don't think it is just Tesla fan-boys that look at the rated range and think it is truth. How many threads have been started on this forum with "Help, my Volt isn't showing anywhere near its rated range" when the first cold spell hits?

The fact that all the ranges on both the Tesla, Bolt and Volt are just best guesstimates based on your latest driving habits and the temperature you last drove in. For example I have seen my Volt increase in range from where it started out as I baby it just shows you that the ranges are constantly changing and anyone who has had an EV for some time knows this.

There is an outfit that drives Tesla's as taxis from Socal to Las Vegas daily. At each destination they would use the Supercharger to charge the vehicles (basically the worst thing you can do to a hot battery). Based on their actual miles driven with supercharging on both ends the owner said he lost 5% in the first 50,000 miles and another 5% in the next 100,000 miles where after 150,000 miles the loss percentage starts to really taper off.

Tesla has tested the batteries to still have over 80% of the range at 500,000 miles.

 

[Ladogaboy]

At each destination they would use the Supercharger to charge the vehicles (basically the worst thing you can do to a hot battery).

Why would that be bad? The TMS should keep the battery at a safe temperature, and the car shouldn't allow the charger to push power to the battery faster than it can be cooled. Or am I missing something?

 

[kns]

It was my understanding that GM didn't cover normal degradation either. Are you stating that when the Bolt doesn't match the same range when it was bought that GM will somehow cover the loss of miles and give you a new battery?

I stated only that I found the paragraph interesting. What I found interesting about it is that Tesla considers a 2016 90D that can be charged to only 70-73 kw-hrs and has suffered range reduction from 270 down to 200 miles to be operating normally. You are welcome to read into the paragraph whatever you like and to draw your own conclusions but please don't put words in my mouth.

KNS

 

[Bluesideup]

Why would that be bad? The TMS should keep the battery at a safe temperature, and the car shouldn't allow the charger to push power to the battery faster than it can be cooled. Or am I missing something?

The TMS does keep the temperature down but the faster the charge the more damage each individual cell can take and when you are charging as fast as the Superchargers can coming right off a hot run that makes for the most challenging state a battery can be in. So, if degradation is going to happen that is the time it will.

 

[Bluesideup]

I stated only that I found the paragraph interesting. What I found interesting about it is that Tesla considers a 2016 90D that can be charged to only 70-73 kw-hrs and has suffered range reduction from 270 down to 200 miles to be operating normally. You are welcome to read into the paragraph whatever you like and to draw your own conclusions but please don't put words in my mouth.

KNS

I don't think I was putting words in your mouth when you implied that somehow GM battery policy was better and you were glad you bought one. "Elsewhere in the thread it is stated that the battery warranty is not applicable to normal degradation, only to excessive degradation. Ouch. I am very happy to own a GM EREV instead of a Tesla BEV. "

Can you please tell me how much degradation that GM allows before replacement of their batteries?

The fact is you're commenting on a comment of an anonymous poster who is using a made up algorithm to try and estimate his battery capacity. The article that actually has data to back up their conclusions clearly shows that is not standard. Then to further regurgitate the anonymous posters comments on message boards like this will only continue to spread misinformation that isn't backed up by anything.

He even says in his first sentence "Every part of this data and conclusions relies on a single completely unreliable assumption".

You can be glad you bought a GM EREV instead of a Tesla BEV but not because of any different battery degradation or warranty.

 

[DonC]

The TMS does keep the temperature down but the faster the charge the more damage each individual cell can take and when you are charging as fast as the Superchargers can coming right off a hot run that makes for the most challenging state a battery can be in. So, if degradation is going to happen that is the time it will.

Seems logical but may not be the case. Discharging at the same rate would create the same heat, and during discharge you may not have the same TMS ability. Idaho National Labs tested the Leaf battery and found that DC charging didn't degrade the battery faster than AC charging. That was consistent with anecdotal evidence from Leaf owners. On the other hand, driving the Leaf in hot temperatures had a pronounced effect. (Note the Leaf has no TMS).

 

[Ladogaboy]

Can you please tell me how much degradation that GM allows before replacement of their batteries?

This thread in another forum [www chevybolt org] has a pretty nifty breakdown:

www.chevybolt.org Link

 

[kns]

I don't think I was putting words in your mouth when you implied that somehow GM battery policy was better and you were glad you bought one. "Elsewhere in the thread it is stated that the battery warranty is not applicable to normal degradation, only to excessive degradation. Ouch. I am very happy to own a GM EREV instead of a Tesla BEV. "

Can you please tell me how much degradation that GM allows before replacement of their batteries?

The fact is you're commenting on a comment of an anonymous poster who is using a made up algorithm to try and estimate his battery capacity. The article that actually has data to back up their conclusions clearly shows that is not standard. Then to further regurgitate the anonymous posters comments on message boards like this will only continue to spread misinformation that isn't backed up by anything.

He even says in his first sentence "Every part of this data and conclusions relies on a single completely unreliable assumption".

You can be glad you bought a GM EREV instead of a Tesla BEV but not because of any different battery degradation or warranty.

I've owned two Volts since since late 2011 and have seen no reduction in energy available from the battery or in actual AER. Nor can I recall any Volt owners reporting significant loss of range that wasn't remedied under warranty. I compare that to the experience reported by this particular 2016 90D owner. But, hey, as I said, you are welcome to draw your own conclusions.

KNS

 

[flyingsherpa]

The TMS does keep the temperature down but the faster the charge the more damage each individual cell can take and when you are charging as fast as the Superchargers can coming right off a hot run that makes for the most challenging state a battery can be in. So, if degradation is going to happen that is the time it will.

I wouldn't call normal driving a "hot run"... I'd think worst case scenario would be an unplugged extended hot soak in high ambient and then trying to supercharge. But I'm pretty sure the car will limit charge rate if the pack is (getting) too warm, just as it limits rate if it's too cold.