Today is the first class of our new March class period. The start time for our class will be 10:00am. We will begin class with a casual conversation. Our reading today is about Baiju. Please try to read as much as possible. Underline any words or sentences that are unfamiliar. Our listening is about batteries. We will finish with our grammar sentences.
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How long do electric vehicle batteries actually last? Back in the early days of the modern EV, there was a real fear that the answer was not that long and that they would need to be replaced midway through owning a car. The good news is those expensive batteries seem to keep going and going. NPR's Camila Domonoske reports.
CAMILA DOMONOSKE, BYLINE: That worry that batteries would be short-lived, it wasn't unreasonable. Batteries do age and hold less power. And unlike the little lead-acid starter batteries in gas cars, a giant lithium-ion battery costs thousands of dollars. Norman Hajjar, who works for the EV drivers app PlugShare, was an early adopter. He got his Tesla Model S back in 2013, when that landmark vehicle was just redefining what EVs could be. And as for that battery?
NORMAN HAJJAR: I mean, there was really no way of knowing what the future held for it because there was zero track record.
DOMONOSKE: In 2010, The New York Times estimated EV batteries would last, quote, "upward from seven years." Well, Hajjar has put nearly 200,000 miles on his Model S, coming on 12 years now on a single battery, and it drives great.
HAJJAR: The car was originally rated to have 265 miles of range. It now has around 220, so the amount of degradation is pretty minor.
DOMONOSKE: Today, there's enough data emerging to say, good news - batteries are lasting longer than anybody thought. Now, batteries do sometimes have defects. Hajjar actually had his replaced in 2014, very early on, so it's a bit younger than his car. But that kind of bad luck is covered under warranty. As for normal aging, let's look at that data. Adam George works for Cox Automotive, which runs big wholesale auto actions. He says they'd expected to see batteries really degrade, even in really new cars.
ADAM GEORGE: What we have seen, though, is that these 2-, 3-, 4-year-old off-lease cars that are coming back have battery health scores well upwards of 95%, which is solidifying that batteries are standing the test of time.
DOMONOSKE: Cox Automotive has tested nearly 80,000 used EVs of all ages. The average battery health score overall was 92%. That's good. But averages can be misleading. So what about just the oldest cars? Liz Najman is the director of market insights at Recurrent, a research firm that pulls in data from over 30,000 EV drivers. Now, she warns that the dataset of old EVs is pretty small, but based on their community, for EVs a decade old and up, more than 90% are still driving on their original battery.
LIZ NAJMAN: What we know is that EV batteries are holding up phenomenally well.
DOMONOSKE: Hajjar's experience sure looks like the rule, not the exception. Now, why exactly did these batteries last so much longer than expected? Well, one, kudos to the engineers. And two, the way batteries are tested is actually tougher on them than real life. Simona Onori is an associate professor at Stanford University. She says batteries are normally tested by cycling them very quickly from a high state of charge to a low state of charge. All the way up. All the way down.
SIMONA ONORI: Whenever you are, you know, on off, on off, it is lots of stress, right?
DOMONOSKE: But when you're actually driving, you never slam the accelerator to the floor and keep it there until the battery is dead, right? It's a lot more varied.
ONORI: We accelerate. We decelerate. The battery will be charged and then discharge. Some rest if you're at a traffic light.
DOMONOSKE: Stanford found if you test batteries in ways that are more like actual driving, they last a lot longer. Onori says real-world data is now confirming those lab results - that when they're actually driven...
ONORI: Those batteries age gracefully. Very gracefully.
DOMONOSKE: Meanwhile, the systems that take care of batteries keep getting better. A lot of new EVs have a different battery chemistry that lasts longer. So we still don't know how long exactly batteries being made now will last. But the new expectation, increasingly, is that they should outlast the cars themselves. Camila Domonoske, NPR News.