Battery Health Survey

Another independent self reporting study is available about the battery life of the Model S.  This new data again shows that the Model S batteries are holding up well.  The average Dutch Model S owner with 30,175 miles reported a rated range of 238 miles on a 85kWh battery.

From the Netherlands, Merijn Coumans is maintaining an ongoing record of the Model S battery life.  He has gathered his information via the Dutch-Belgium Tesla Forum.  You can access the file yourself. This data contains information from 109 owners.  All but five owners reported results recently with firmware 6.0 or higher.  Only six of these owners have a 60kWh battery.  None of the European Model S cars have the A battery, and all but five owners reported results on version of V6.0 software or later.  For more charts and analysis, you can read a report from my fellow blogger, Maarten Steinbuch.

I had done a similar survey in 2013 with similar degradation results over time.  My goal for that survey was to determine if driving habits had much influence on rated range.  The survey debunked that rumor.

This second survey again shows two main facts.  First the Tesla batteries are holding up well and only degrading by an around 6% at 50,000 miles..  Secondly, measuring this data on your own car is a bit challenging as there are several things that can affect the number.  How recently did the car have the battery drained to near zero and filled back up completely?  On my cross country trip last spring I noticed my rated range go up as I had fully charged the vehicle several times.

I have now switched my car over to display a % number of charge left not the rated range value.  I have really no concern about battery degradation at this point.

CA Rebate Survey

California gives every electric vehicle owner a rebate when buying their car.  They also recently sent a demographics survey from the Clean Vehicle Rebate Project in order to understand the buying process.  The survey consisted of about thrity questions.  And fortunately, you can skip any question you are not comfortable answering.

The survey is a typical marketing survey with reasonable questions.  They were also trying to asses whether the EV buying experience addressed issues such as electricity rates, range, home charging etc… The whole survey was well written but a little unusual for someone like me who was actually replacing one EV for another.

Green Button

Federal Green Button Program

The survey also requests the buyers to download their Green Button energy use data.  I had never heard before of the Green Button program. The effort is from the utilities in response to a White House call to action. The personal energy usage data is standardized in a consistent and machine-readable form.  The end user can use the file or send it to a third party such as the Clean Vehicle Rebate Project.

The data in the green button program is not any different than the other data I have churned through before to figure out my energy usage.  But hopefully some sort of standardization will enable third party developers to help us use energy more efficiently and help us analyze trade-offs of different rate plans.

Two questions I found the most interesting and I would like to see the results from the general population that would be questions 14 and question 15; both questions address the motivations for buying an electric car.  I was a very early adopter of electric vehicles because of my concern about the environment.  Since the Model S is such a fantastic car, many people are buying the car for performance reasons.  I have also heard that it is the ‘it’ prestige car and a ‘status symbol’ now here in Silicon Valley.  I also recently heard someone (likely with some envy or other issue) in a crowd disparage Tesla owners claiming they were environmentalists;  I chose not to respond.

Question 14

Question 14

Question 15

Question 15

Tesla Best Seller $Zip

Edmunds published an interesting new report on the success of the Model S in wealthy zip codes in the U.S.  Since zip codes are typically smaller than many cities, the zip code correlation is typically more local and representative.  Edmunds concluded the following:

  1. Tesla is doing very well in the zip codes with the highest home values.  Eight out of twenty five of the top zip codes had the Model S as the most popular vehicle purchased.
  2. Tesla’s US market penetration is 0.1%.
  3. The Model S is not the most expensive car in the market, so there is not a direct correlation between ‘most expensive home’ and ‘most expensive car’ purchases.
  4. Edmunds is very popular with the Silicon Valley set with four zip codes with double digit market share from 15.4% to 11.2%:  Atherton, Los Altos Hills (2 zips), and Portola Valley.
  5. Outside of California, the highest market share was only 1.2% in Watermill, NY.
  6. Other popular vehicles are Mercedes and Jeeps.

What the article did not point out was that all eight of those twenty five zip codes where the Model S is the best selling car model are in California!

Tesla Model S Top in Market Share in 8 Zip Codes in California

Tesla Model S Top in Market Share in 8 Zip Codes in California

Rated Range Ranges

After publishing the Rated Range Survey results, I got some interesting responses on the forums.  I did not hear anyone still arguing that rated range is dependent upon driving habits.  Also there seems to be a consensus that rated range can vary from day to day and also is not particularly predictable.  The thought is that to truly judge your battery, a complete charge is required.  I just avoid these charges unless I truly need them for an unusual long distance drive.

Outliers Likely Did a Compete Charge

Outliers Likely Did a Compete Charge

One person pointed out that most of the errant 85kWh data I had were from folks who did a complete charge as those numbers were all in the 265 to 277 range;  I have circled that data in the graph.  I somehow did not catch that in my analysis.  So the only true outlier is the person who reported a 203 range.

Although it seems a bit early in the lifecycle of the Model S, Plug in America is running a survey about battery degradation.  I am going to fill this form out even with my inaccurate full “daily” charge.

In the process of filling up my battery, I found an unusual situation where one morning it did not completely fill up but stopped a hair short as the picture shows.  I tried to “top it off”, but the software would not continue to fill the battery.  The next morning, I did the same process and the screen showed the battery completely filled up to the “daily” limit with almost the same rated range.

Almost Full

Almost Full

Rated Range Results

A debate has existed about the Rated Range value in the Tesla Model S.  The number appears to vary quite a bit from car to car.  Some Tesla employees have told customers that the number does depend upon driving habits.  Other Tesla drivers have claimed that these employees are misinformed and the number exclusively depends upon the state of charge of the battery, and perhaps would be worried if their number was lower than another driver’s Rated Range.

In order to answer this question, I surveyed the owners with the following five questions:

Q1: What is your rated range after a full non-range mode charge?

Q2: What is your Average Energy for your car? This info is under Controls / Trip. Please provide the data for the longest distance trip available.

Q3: What is the Distance given in the “distance column” in the same line?

Q4: What version of OS is your Model S on? 4.4 ? 4.5 ? Don’t know?

Q5: Is your Model S battery 60kwH or 85kwH?

To attempt to answer this question, I surveyed Tesla drivers and received sixty three respondents, two were 40 kWh battery owners.  Fifteen of the respondents own the 60kWh battery version.  The data from this smaller set is a bit more straightforward than the data from the 85kWh battery.

One small problem with the survey is I am assuming there is a strong correlation between the “distance column” and the car mileage.  Ideally, I would have asked another question about the vehicle mileage.  Since the cars have been in full production for less than a year, I am not expecting dramatic battery degradation or very many high mileage vehicles.  I also assumed most owners would keep either Trip A or trip B as the full vehicle mileage in order to get a gauge of their true kWh energy usage.  I have maintained trip A for this purpose because in the Roadster there was no other method to measure how much energy I used over the lifetime of the vehicle.  Regardless, I think there is a correlation between the distance reported and the car’s mileage in most cases.

A few respondents also answered they either did not know their OS version or were using version 4.4.  Eliminating these data points did not significantly change the graphs below.

First, lets look at the data for Rated Range vs. Distance in a 60kWh battery.  For this battery, there seems to be perhaps a small amount of battery degradation for the high mileage driver with around 15,000 miles is getting a rated range of 178.  Interestingly this individual is also driving the most conservatively (or energy friendly) of the the 60kWh battery group using only 291 Wh / mile.  A total of seven respondents managed to achieve under 300 Wh/mile.

Rated Range vs. Distance 60kWh Battery

Rated Range vs. Distance 60kWh Battery

The rest of the statistics seem to indicate no appreciable difference in mileage for the 60 kWh batttery before 10,000 miles and no correlation appears to exist between rated range and mileage.  Also for the 60 kWh battery there seems to be no correlation between range and energy.


Rated Range vs. Energy Wh/ Mile 60kWh Battery

Rated Range vs. Energy Wh/ Mile 60kWh Battery

Looking at this small set of data for the 60 kWh battery there seems to be little correlation between rated range and driving habits, which would be reflected in energy usage, and too little data to indicate any problems with battery capacity.  The “range” of rated range for a 60kWh battery is between 175 and 195 for unknown reasons.  The two data points for the 40kWh battery was 140 and 143 rated range.

The data set for the 85 kWh battery is larger with 47 responses.

Rated Range vs. Distance 85kWh Battery

Rated Range vs. Distance 85kWh Battery

In this data set the results are for the most part consistent with the rated range within a band of 220-245.  The outliers are a bit perplexing.  All but one reported a very high rated range near 275 are on 4.5 or above operating systems and have vehicles with at least a couple thousand miles on them.  Their energy / mile usage varies.  One vehicle reports a rated range of 203.  This 203 rated range vehicle does not have a particularly high energy consumption per mile.  The data could be an errant typo in the survey, a non-full range charge or a problem with the vehicle.


Rated Range vs. Energy / Mile 85kWh Battery

Rated Range vs. Energy / Mile 85kWh Battery

This final chart shows the same lack of relationship rated range and energy.  The few outliers in the chart are the same outliers in the earlier chart.

I think this question is still perplexing as the range values vary a lot from car to car for mysterious reasons.  Why would a 85 kWh battery have a rated range between 220 and 245?

I think this survey almost asks more questions than it answered.  There is clearly not a clear correlation between long term driving habits and rated range.  Perhaps immediate short term driving habits?  Or perhaps the car simply cannot measure the amount of energy in the battery very accurately.  Also how accurate, reliable and useful is this rated range number?  Why is there so much variation in the rated range number in the Model S?

I did experiment with merging the data to see if there was a weighed factor equation between the two.  After some experimentation, I could not significantly improve the chart to demonstrate any useful information.

What I would personally like to see is an accurate consistent rated range that I could understand and also a simple energy measurement.  I would like a gauge that simply said 55kWh left in my battery.  I would find this more straightforward.  I can do the simple math in my head to convert that to “can I drive to X without recharging”.

I am also wondering if part of the problem with giving these accurate numbers is that historically cars do not give you accurate measurements of remaining fuel.  All of the cars I have owned have had crude analog gauges or digital readouts that were stepped scales not a simple numeric readout “12.1” gallons left.

I am looking forward to any comments on this survey.


Rated Range Survey

In an attempt to answer the question “Is rated range related to driving habits?”  We have heard from Tesla employees that there is a correlation, some drivers say no.

Please fill out this five question survey monkey after charging up your car. A summary of the data will be provided to this blog once collected. Thanks!

Rated Range and Average Energy Tesla Model S Survey

These are the five questions you will see.

1. What is your rated range after a full non-range mode charge?
2. What is the Average Energy for your car? This info is under Controls / Trip. Please provide the data for the longest distance trip available
3. What is the Distance given in the “distance column” in the same line?
4. What version of OS is your Model S on? 4.4 <enter 4>, 4.5 <enter 5>, don’t know <enter 0>
5. Is your Model S battery 60kwH or 85kwH?