Battery Study Updates

At Plug In 2013 in San Diego, I presented some new and updated results from the Plug In America EV battery longevity studies.

The Original 1997-2003 Toyota RAV4 EV

First up, let’s take a look at a chart showing results from 62 original RAV4 EV owners. These vehicles started production in 1997 and leased as fleet vehicles. In the 2002 and 2003 model years, around 300 were leased or sold to consumers. The majority of those vehicles are still on the road today. They use nickel metal hydride batteries and provide over 100 miles per charge.

The horizontal axis shows the vehicle age and the vertical axis is the odometer reading. The blue dots are vehicles that are still driving on their original battery packs and the red diamonds have had their battery packs refurbished.

RAV4 EV odometer versus age by battery pack status

As you can see, these vehicles are lasting as much as 150,000 miles and 12 years on their original batteries. One intrepid owner has driven nearly 250,000 miles with a refurbished battery pack.

Tesla Roadster

In July, I released results from our Tesla Roadster battery study at Teslive. From the data collected at that point, the data suggested that the average Tesla Roadster will have between 80% and 85% of the orignal battery capacity (range) after 100,000 miles. Since then, one survey participant has crossed the 100,000 mile line within the expected range.

This graph shows the distribution of age and odometer readings among the Roadster survey participants.

Tesla Roadster odometer versus age by battery pack status

Below is a graph showing the battery capacity levels of the Roadsters still driving on their original battery packs as a percent of the original expected capacity.

Roadste capacity vs odometer

Tesla Model S

The Tesla Model S is barely a year old, so it seems pretty early to be doing a battery survey, but the owner community expressed interest so we started one up. The Model S comes with three different battery pack sizes: 40, 60, and 85 kWh. (The 40 kWh option was canceled, so only a few were sold.)

Let’s start with a graph showing the population of Model S survey participants by age and odometer, with the data points colored by battery pack size. Notice the Model S owner who has driven over 32,000 miles in less than a year!

Model S age and miles

To examine battery capacity over miles driven, the graph below shows just the 60 and 85 kWh vehicles in separate groups.

Model S capacity by odometer

So far, we’re seeing a little variation between vehicles, but basically flat performance over miles with no discernable degradation. Stay tuned for more results as we see more years and miles on these vehicles.

Driving Trends

One thing that has emerged from the battery surveys that I wasn’t originally looking for is how much owners of different models drive their cars. For each of the four survey, I’ve added up the total number of miles driven and divided by the sum of the vehicle ages to get an average number of miles driven per year of ownership.

miles per year by model

I suspect the RAV4 EV miles per year are reduced as many of those owner have picked up one of the newer EVs and shifted at least some miles away from the RAV. The same is true of the Roadster population as many of those owners have picked up a Model S. Still, it’s interesting how similar the RAV4 EV, LEAF, and Roadster populations are in how many miles they drive.

However, Model S owners are driving their cars substantially more. When comparing to the LEAF and RAV4, the Model S and Roadster have approximately the same range capability. Perhaps it’s the availability of Supercharging, the increased passenger and cargo space, or differences in the ownership demographics, or a combination of all three, that is enabling the Model S owners to drive well above the annual average for gas cars.

Stay tuned for more results as we continue to gather information from the EV owner communities. If you are driving one of the survey models, please visit the battery survey page to get more information and contribute your electric driving experience.

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