Tesla battery researcher shows new test results pointing to batteries lasting over 2 million miles

A Tesla battery researcher showed updated test results pointing to batteries lasting over 15,000 cycles or the equivalent of over 2 million miles (3.5 million km) in an electric car.

Last year, we reported on Jeff Dahn and his lab, who is under contract to do battery research for Tesla, releasing a paper that shows how the latest Li-ion battery technology can produce batteries that would last 1 million miles in electric vehicles.

In a new presentation, Dahn discussed updated test results from this new battery, which he hopes becomes the new standard Li-ion battery against which new battery technologies benchmark themselves.

The scientist, who is widely recognized as a pioneer in Li-ion batteries, referenced our article from last year about their paper and said that it sparked a massive interest in this new battery chemistry and battery longevity.

They have continued testing those batteries with some of them going on three years of testing and over 10,000 cycles:

Dahn now concludes that these batteries in a medium-range electric car would be able to last over 3.5 million km or over 2 million miles.

He also showed results based on different depths of discharge, which means to what percentage of capacity they are discharging the batteries before recharging them, and it showed the Li-ion batteries performing extremely well after up to 15,000 cycles so far:

Most impressively, the batteries show very little to no capacity degradation when they are discharged between 25% to 50% of their capacity, which is actually how most people use their cars.

On average, American drivers use their vehicles for less than 30 miles per day.

For example, with this battery in a Tesla vehicle with over 300 miles of range, you could use it to commute 30 miles a day and by charging, on average, from 70 to 80% every day, it would result in very little to no battery degradation.

Considering it would mean those batteries could virtually last forever or much longer than the actual useful life of a car, Dahn brings up the question: do we actually need batteries that are that good?

Tesla CEO Elon Musk has been saying that they plan to have batteries that would last more than 1 million miles for the automaker’s “robotaxis,” which are going to have a much higher utilization rate than consumer vehicles.

Musk has also mentioned in the past how longer-lasting batteries are critical for other Tesla programs, like Powerwalls, Powerpacks, and Tesla Semi electric trucks.

Dahn also brings up that these new super long-lasting batteries could be useful to enable vehicle-to-grid features.

In the past, Tesla has been reticent in enabling owners to use the batteries inside their cars to discharge energy into the grid due to the impact on battery longevity, but these new batteries would fix those issues.

Interestingly, Drew Baglino, one of Tesla’s top engineering leaders, has recently mentioned that future Tesla vehicles will have bi-directional chargers enabling vehicle-to-grid or vehicle-to-everything technologies.

Dahn brought up several other interesting potential uses of batteries with extreme longevity and briefly commented on Tesla’s “Battery Day” in the presentation:

Tesla is moving forward at the speed of light. They are upscaling their factory. They know they are going to need terawatt-hours of batteries for both energy storage and vehicles. It’s an incredibly exciting time.

Here’s Jeff Dahn’s new presentation in full:

Electrek’s Take

Very impressive new test results here.

It’s especially interesting since longevity is not something Tesla talked a lot about during the Battery Day presentation.

It focused mainly on cost and scale, but Tesla has been guiding for a while now that they are making great improvements to longevity, and a lot of those improvements seem to be coming from Jeff Dahn’s lab.

Older Tesla vehicles have already showed only limited battery degradation, and in general, batteries in Tesla vehicles seem to be holding up pretty great already, but it’s fascinating to think that in the near future, longevity could be so great that it enables new features and different use cases.

As usual, Dahn is not disclosing whether or when Tesla is implementing these changes, but with the company now making its own cells, I wouldn’t be surprised if the Tesla 4680 cells feature some crazy longevity.