Here’s one way we know an EV’s battery lasts the entire life of the car

Here's one way we know an EV's battery lasts the entire life of the car
enlarge An EV’s battery represents a whopping 25 percent of the cost of the car, so it’s understandable that people are nervous about longevity.

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It is often said that the easiest way to get people to buy an electric car is to test drive one. But here in the US only EVs were good for 3 percent of the 15 million new vehicles sold in 2021. That means there are an awful lot of misconceptions when it comes to these newfangled machines.

Probably the biggest concern is range anxiety, a fear that is usually allayed once a person gets used to waking up every morning with a full battery. I won’t dwell on that today, but the next most common point of confusion about EVs has to be traction battery life, or the possible lack of it.

It’s an understandable concern; many of us are used to using consumer electronics powered by rechargeable batteries that develop a so-called ‘memory’. The effect is caused by repeatedly charging a cell before it is completely empty, causing the cell to “forget” that it can further deplete itself. The lithium-ion cells used by EVs aren’t really affected by the memory effect, but they can reduce storage capacity if overcharged too quickly or if their thermal management isn’t taken seriously.

The Nissan Leaf bears a lot of responsibility for the idea that EV batteries don’t last. Nissan eschewed liquid cooling for the Leaf package, and the EV first went on sale in the 2012 model year, so there’s been plenty of time for some early Leafs to lose up to 20 percent of their packs storage capacity

Most EVs are not the Nissan Leaf

It turns out that an EV’s battery pack is subject to a stricter warranty than the rest of the car — federal law requires automakers to provide a minimum of eight years, or 160,000 miles, on packs. And with the exception of Nissan, every EV for sale today comes equipped with liquid battery cooling as part of its battery management system.

Tesla has been making electric cars for so long that some of its cars have racked up huge miles. providing real world data about degradation over time. EVs from OEMs newer to the electrified end of the market must instead rely on extensive testing programs to determine if their battery packs have what it takes for the long haul.

Some of those tests involve actual cells combined into modules, repeatedly charging and discharging them over weeks, months, or even years in temperature-controlled test chambers. But simulation can save costs and development time.

“Often, when you’re testing early, sometimes you don’t even know what to test. But simulation can give you some of these insights from a physics point of view or from a design behavior,” said Pepi Maksimovic, director of application engineering at Ansys , which provides simulation tools to the automotive industry. “There are four primary failure modes: thermal failure, mechanical failure – because they shake and vibrate and break the solder, and so on – humidity and dust; and all those effects can and are modeled,” she told me.