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How long will my EV battery last? California proposes degradation limits

How long will the battery in this used EV last?

Given how quickly the batteries in smartphones and laptops deteriorate, it’s easy to see why used EVs can be a cause for unease.

Those buying pre-owned EVs—perhaps even more than the original buyers—need to have confidence they can replace gasoline vehicles with electric vehicles that come close to their original rated range and performance. And those who choose to keep driving the EV they bought new shouldn’t face a dramatic degradation in usefulness after seemingly normal use. 

Because a long battery life is so important in realizing the environmental benefits of EVs, regulators are stepping in. Provisions for defining EV battery health are part of the Advanced Clean Cars II framework that the California Air Resources Board (CARB) presented for the first time earlier this month—a measure that aims to make EVs 80% of new light vehicle sales by 2035

The rules would require that BEVs maintain 80% of their certified test-cycle range for 15 years or 150,000 miles, while fuel-cell models maintain at least 90% output power after 4,000 hours of operation. 

CARB proposal - battery durability

CARB proposal – battery durability

The requirements would also include the explicit disclosure of that percentage threshold and a “customer readable state of health metric,” according to the CARB draft. The state of health (SOH) needs to be readable by the driver without a tool and meet the “usable battery energy” as met by SAE J1634 standards, with the vehicle maker clearly laying out the SOH percentage that qualifies for warranty repair. 

Under the new rules, warranties for the batteries in BEVs would also be required for 10 years or 150,000 miles—the same duration of a defects-and-performance warranty already required of batteries in plug-in hybrids according to CARB rules. 

Nothing like this exists today in the U.S. for battery electric vehicles. And the ramifications extend not just to those who drive EVs but those who potentially repair them. Aiming perhaps at making sure maintenance is accessible, the rules would require “information disclosure for all propulsion-related components,” with standardization for communicating with the vehicle and reading propulsion-related fault codes. 

Tesla Model Y

Tesla Model Y

That’s a condition that potentially relates directly to the “right to repair” movement that Tesla continues to oppose

CARB’s battery rules make sense. As battery cell manufacturing is especially carbon intensive, a vehicle is likely to have a lower carbon footprint over its lifetime if the battery pack lasts the entire lifetime—and, perhaps, has a second-life purpose in energy storage or industrial equipment. 

David Reichmuth, the senior engineer in the Clean Transportation Program at the Union of Concerned Scientists, sees that the proposal serves both as a consumer protection and an environmental assurance. California, he says, “has an interest in making sure that EVs are capable, and that consumers don’t have concerns over buying a used EV and being able to replace a gasoline vehicle.”

The consumer advocacy organization Consumer Reports appears to agree with the latter sentiment. “CR welcomes the new electric vehicle durability requirements to ensure consumers have access to long-range, long-lasting vehicles,” it said in response to the rules proposal. 

According to Reichmuth, it all comes back to ensuring longevity for the batteries and helping make sure we get the most benefit out of the vehicles. 

Simply put, there are increased emissions in making a battery electric car versus a gasoline one, but those emissions are offset pretty quickly by the emissions savings in using the EV. “The longer we use that electric car, the more savings we can accrue,” he said. 

General Motors' BEV3 platform and Ultium batteries

General Motors’ BEV3 platform and Ultium batteries

There’s definitely momentum in the industry to produce cells that potentially outlast the cars. Tesla CEO Elon Musk in 2018 said that Tesla might soon offer a battery pack capable of a million miles or more. Last year the cell supplier CATL said that it was “ready to produce” a battery pack that will last 16 years or 2 million kilometers (1.24 million miles) for any interested automaker. And last year General Motors global electrification and battery director, Tim Grewe, said that GM has “million-mile battery life, especially in shared mobility usage, in our sights.”

As much as long-lasting batteries might be in the interest of automakers, there are definitely some examples of EVs with cells that haven’t lasted anywhere close to those CARB targets. Earlier Nissan Leaf models are prime examples; it’s not unusual to see a 10-year-old Leaf with 75,000 miles—half the target—limited to well under 80% of its original capacity. But in the era of liquid-cooled batteries, this is expected to be increasingly rare. 

CARB proposal - battery labeling

CARB proposal – battery labeling

CARB also proposed a new protocol for battery labeling that might make it easier to sort vehicle battery modules and allow easier repurposing or second-life uses. 

How can we displace the most gasoline- and diesel-powered vehicles as soon as possible? By having EVs that keep their original function and build confidence. It sounds like California is on the right track. Let us know what you think—and don’t hesitate to check in with CARB, which is accepting written comments through June 11, 2021, prior to a vote on a more detailed version of this proposal expected later in the year. 

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