For Used Electric Vehicle Buyers, Battery Health Is Everything. And There's No Way To Know It

The battery is the most important part of an electric vehicle, but there's currently no way for used car buyers to find the battery's state of health.
June 9, 2021, 1:00pm
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In November of 2019, George Churchill was in the market for a used electric vehicle. He didn't know anything about electric cars except that getting one would give him a sticker to use the HOV lane in his home state of Maryland and cut his commute time. One day after work, he went to a local Nissan dealer and tested a used 2016 LEAF. 

On the LEAF's dashboard display next to the charge level was a meter of 12 bars indicating the health of the car's battery, with 12 being perfect health and zero being the battery cannot hold a charge. Despite being three years old, the LEAF Churchill test drove had all 12 bars, meaning it could hold close to the maximum amount of charge and therefore drive the car's full advertised range. Churchill bought it the next day for about $16,600.

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But Churchill noticed something was wrong on his drive back home. When he left, the car estimated it had 80 miles of range. By the time he finished his 25-mile commute, it said it had 30 miles of range left. And in the next few days, Churchill said the battery health meter lost two bars. When he called the dealer to complain, he was shuffled between departments and ultimately ignored.

After doing some research, Churchill learned the battery health meter can be reset using a car diagnostic tool. After resetting, the meter will display all 12 bars for a short period before recalibrating after some use, just as Churchill's did. During this time, the car is essentially lying about its battery health.

"I still feel like I was cheated," Churchill told Motherboard. "I enjoy driving it, but the limited range has been bad enough that I often think about going back to a gas car."

Churchill's experience highlights a major but underappreciated challenge facing widespread electric vehicle adoption. While most of the conversation has focused on new car sales, of which there are 17 million in the U.S. per year, relatively little attention has been given to the used market, where more than 40 million total vehicles were sold in 2019 according to the Bureau of Transportation Statistics. In order for electric vehicles to permeate the U.S. vehicle landscape as quickly as possible, they need to not simply take over the new car market, but they then need to get absorbed by the used market as well, which will make them available to buyers who can't afford a pricey new EV. Lots of car buyers never even consider new cars, which retail for an average of $38,000. And even for new car buyers, the used market is important, since resale value is often one factor they consider. 

The process of evaluating a used car's prospects is completely different for electric cars than for gas cars. Electric vehicles are basically giant batteries on wheels. Typically, they are lithium ion batteries or a substantially similar chemical composition, and anyone who has owned a phone or laptop over the last decade knows lithium ion batteries lose their charge with repeated use, a problem that doesn't have an analogous situation with gas cars.  In other words, there's no way to truly evaluate the condition of a used EV without knowing the condition of the battery. But there is currently no way for used car buyers to do that.

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That being said, many EV brands have shown remarkably resilient batteries, at least insofar as we can tell. According to Tesla's sustainability report, Model S and X batteries retain well above 80 percent capacity even after 200,000 miles travelled, and typically hover closer to 90 percent capacity (Model 3's haven't been on the road long enough to evaluate). And while it is harder to give overall numbers for other manufacturers which don't provide similar data, anecdotal reports suggest Chevy Volt, Spark, and Bolt batteries are holding up pretty well, as does the BMW i3.

The irony of Churchill's experience is the LEAF is the only electric vehicle for sale in the U.S. that even has a battery health meter customers can view. Every other electric vehicle currently restricts that information to proprietary devices that typically only the sellers or dealers have access to. 

"It's tough to be an informed shopper going to buy a used [electric] car when the thing of the most value on the entire car is the battery pack," Vehicle Program Specialist Mike McCarthy at the California Air Resources Board told Motherboard. The end result is serious EV shoppers end up spending months giving themselves crash courses on battery management and warning signs for premature degradation, which can only do so much to avoid a deceptively degraded battery.

This isn't to say all EV batteries have problems. Far from it. In fact, the LEAF is notorious for being the major outlier with battery degradation issues because it doesn't have an active battery temperature management system, resulting in more rapid degradation. It is not a coincidence, McCarthy said, that the LEAF is the only EV with a battery health indicator consumers can see, because it's in response to a known issue. And while there are some legitimate cases in which it makes sense to reset the battery health meter, such as when replacing the battery, McCarthy said Churchill's case is not the first time he has heard of that feature being abused by scrupulous used car salespeople.

There is precious little solid information for potential used EV buyers. Nicholas Pankewytch was shopping for a used EV in Massachusetts when he went to a Kia dealer who showed him a 2016 Soul EV that had four percent battery charge at the time. The dealer told him they regularly let the battery drop to zero, which, in Pankewytch's words, was "a huge red flag," as letting a battery fully deplete is generally bad for its long-term health. Based on a tip he saw on a Reddit forum, Pankewytch said he wouldn't buy the car unless he could see it when charged at 100 percent, at which point the car would display an estimated range, a number that is typically the best ballpark for battery health. The dealer refused. But Pankewytch saw that even with four percent charge, the car estimated just three miles of range. He projected that out to a full charge and suspected the battery had significant degradation. He ended up buying a new 2020 Kia Niro EV instead from a different dealer.

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Nick Abel said battery issues were "definitely" on his radar when he was shopping for a used EV near Indianapolis, Indiana. But he ended up having to do all his own research because the dealers he contacted wouldn't talk about it at all unless asked specific questions. For Teslas, he would ask the seller to take photos of the estimated range at 90 and 100 percent charge. For LEAFs, he asked to see the battery state of health bars. Still, he knew that there "doesn't seem to be foolproof ways of knowing on any of these cars" without having access to the internal diagnostic tools. In the end, he bought a BMW i3 from a private seller who Abel was confident had taken good care of the car and was forthcoming discussing battery health.

In some ways, McCarthy said, this is not all that different from buying a used gas car, a practice long associated with deceptive sales practices. In fact, the used car market is typically the literal textbook example for what economists call "asymmetric information," in which one party knows more about the product than the other and therefore the agreed upon price probably doesn't reflect the actual quality of the product in question.

Still, the gas car market has had decades to evolve to reflect this asymmetry of information. Just the fact that people are commonly aware of the pitfalls of buying a used car helps to some degree. Plus, there are car history reports and inspection services that can be purchased prior to the sale to correct this imbalance of information. But these are mostly geared towards how gas cars work and are valued and haven't yet adjusted for the electric car market. In order to speed up the electric vehicle adoption, McCarthy knows that these early adopters, who are often a self-selected group of people willing to do such extensive research prior to the purchase, might not be reflective of the average consumer. There is a role for regulators to play to even the playing field.

To help address this problem, the California Air Resources Board is planning to propose a set of rules. One would mandate batteries maintain at least 80 percent health for 15 years or 150,000 miles. Another would create a minimum battery warranty term of 10 years or 150,000 miles. Yet another proposal would mandate all electric vehicles have clear battery state-of-health information any consumer or prospective buyer can easily access via the car's display, and also require that the same display discloses when a battery is eligible for a warranty repair. And McCarthy said they are considering ways to avoid what Churchill experienced with the LEAF where the meter is reset without the consumer's knowledge. One idea is a requirement to report the mileage since it was last reset or mandating a disclosure for a certain amount of time after it has been reset. But the rulemaking process is a bit slow; McCarthy said it wouldn't be mandated until 2026 at the earliest, but nothing is stopping automakers from doing the right thing sooner.

"In my mind," McCarthy said, "it is definitely addressable going forward and stories like this Nissan one are clear indications that it is prudent for us to step in and take these steps." In the meantime, good luck out there.