Powering Up
Battery developers working for electric automaker Tesla claim to have built a battery pack that could power a car for a million miles.
In April, CEO Elon Musk said that he wants Tesla to crack fully-autonomous driving and launch a fleet of robotaxis. While they won’t help with the many remaining challenges facing self-driving car developers, the batteries could at least stand to make the taxis far more cost-effective, Electrek reports. If it gets deployed, the battery could seriously drive down the cost per mile of operating an electric vehicle — robotaxi or not — helping make clean transport a more viable option for everyday use. it
The Part With Math
Over the last three years, the University of Dalhousie researchers have been testing a new kind of lithium-ion battery that they say can be reliably recharged as many as 6,000 times, according to research published Friday in the Journal of the Electrochemical Society. Over the course of a two-decade shelf-life — admittedly a long time to keep a car — that could add up to more than a million miles traveled on the same battery.
Even under extreme heat conditions, the battery could be recharged about 4,000 times. So even if the ideal million-mile metric isn’t met, the new battery systems could keep future Tesla vehicles running for years at a time.
Tesla’s battery research partner has released a new paper on a battery cell that could last over 1 million miles, which they say is going to be particularly useful in ‘robot taxis’ — something that Tesla wants to bring to market.
When talking about the economics of Tesla’s future fleet of robotaxis at the Tesla Autonomy Event, Tesla CEO Elon Musk emphasized that the vehicles need to be durable in order for the economics to work:
The cars currently built are all designed for a million miles of operation. The drive unit is design, tested, and validated for 1 million miles of operation.
But the CEO admitted that the battery packs are not built to last 1 million miles.
Earlier this year, Musk said that they built Model 3 to last as long as a commercial truck, a million miles, and the battery modules should last between 300,000 miles and 500,000 miles.
However, the CEO claims that Tesla has a new battery coming up next year that will last a million miles.
Jeff Dahn and his lab, who are doing battery research for Tesla, have released test results for an impressive new battery cell that is going to be Tesla’s new million-mile battery, according to a source familiar with the matter.
The new battery tested is a Li-Ion battery cell with a next-generation “single crystal” NMC cathode and a new advanced electrolyte.
Dahn’s team have been extensively testing these cells and based on the results, they think that the battery could power an electric car “for over 1.6 million kilometers [1 million miles].”
Here’s how Dahn’s team describes the results:
We present a wide range of testing results on an excellent moderate-energy-density, lithium-ion pouch cell chemistry to serve as benchmarks for academics and companies developing advanced lithium-ion and other ‘beyond lithium-ion’ cell chemistries to (hopefully) exceed. These results are far superior to those that have been used by researchers modeling cell-failure mechanisms, and as such, these results are more representative of modern Li-ion cells and should be adopted by modelers. Up to three years of testing have been completed for some of the tests. Tests include long-term charge-discharge cycling at 20, 40, and 55°C, long-term storage at 20, 40, and 55°C, and high precision coulometry at 40°C. Several different electrolytes are considered in this LiNi0.5Mn0.3Co0.2O2/graphite chemistry, including those that can promote fast charging. The reasons for cell performance degradation and impedance growth are examined using several methods. We conclude that cells of this type should be able to power an electric vehicle for over 1.6 million kilometers (1 million miles) and last at least two decades in grid energy storage.
We are talking about battery cells that last two to three times longer than Tesla’s current battery cells.
They have tested the battery cells under different conditions and cycles. Even at the extreme temperature of 40’C, these cells were lasting 4,000 cycles.
With an active cooling system, like in Tesla’s battery pack, it was pushing the battery cells to over 6,000 cycles, which would easily mean over 1 million miles in a good battery pack.
Controlling the charge to less than 100% state-of-charge also helps push the longevity.
In the research paper, Dahn’s team especially reference that this new longevity potential would be particularly good for “robo taxis”:
This situation may change with the proposed introduction of “robo taxis,” long-haul electric trucks, and vehicle-to-grid applications. In the former, vehicles will be driving all day, much like a conventional taxi and undergoing nearly 100% DOD cycling. Long haul trucks will almost certainly run in near 100% DOD situations. Cells in vehicles tethered to the grid will be racking up charge-discharge cycles, even when the vehicle is not moving. Clearly EVs destined for vehicle-to-grid applications, robo taxis, or long-haul trucking would favor a lithium-ion chemistry that could deliver many more charge-discharge cycles in a decade than an EV that was destined for typical commuter driving where high energy density to give the longest driving range for weekend trips might be emphasized. Electric buses represent another application where duty cycles approaching 100% DOD are used on a daily basis.
The details of this new battery cell come as we learned that Tesla is working to build its own cell manufacturing line.
Here’s the research paper in full (thanks to Ravindra Kempaiah):
J. Electrochem. Soc. 2019 H… by Fred Lamert on Scribd
Electrek’s Take
This is it, people.
For those doubting Elon when he said that Tesla would have a million-mile battery next year, it is starting to become a lot more likely now.
I think that this new battery combined with the fact that Tesla is moving to manufacture its own cells is a real game-changer.
Tesla is looking years ahead, and I think there are doing the right thing.
In a future where mobility is dominated by fleets of self-driving shared electric vehicles, the cost per mile is going to be way down, and longevity of these vehicles is going to be a big differentiating factor in the cost.
If you really have a car that can last a million miles, you are going to get a lot more value out of it since you are getting revenue per mile from the use of the car.
What do you think? Let us know in the comment section below.
