EV Battery Life

Abstract

Chris and Fred discuss the long-term life of electric vehicles (EVs) and other rechargeable batteries, which tend to be longer than predicted. Why?

Key Points

Join Chris and Fred as they discuss why some rechargeable batteries, like those on electric vehicle (EV) batteries, appear to last longer than what the manufacturers tell us they will. Why is that?

Topics include:

• Laboratory testing often understates real-world use stresses. This often happens when people don’t want their ‘baby’ the wonderful new product they have designed to fail qualification or design review testing. So stresses are understated, ‘on-off’ cycles are ignored, thermal stresses are assumed to be nothing, and so on. But this is not what happens for rechargeable batteries (even though it happens the most).
• Laboratory testing can sometimes overstate real-world use stresses. Most rechargeable battery lives are based on ‘recharge cycles.’ This involves a battery being fully discharged and then fully recharged – quickly. This is chemically stressful … and not what most users do. We routinely plug in our cell phones every night when we go to bed regardless of how much charge is remaining. We often never allow some of our rechargeable batteries to never come close to fully discharging. And this means that batteries last longer. When it comes to EV battery testing, the manufacturers tend to assume the ‘worst use case’ where batteries are fully discharged and quickly recharged. EVs are usually charged every day … regardless of battery state. So the batteries last longer.
• Is getting it wrong a problem? It depends. If you are deliberately and informative being conservative (like the EV battery manufacturers are), then no. You don’t want to be wildly wrong and torture your products in ways that customers and users never will. So you want to research as much as possible, to reduce the uncertainty you have. But there will always be that uncertainty to ‘under promise and over deliver – within reason.’ You don’t want to miss marketing opportunities regarding things like battery performance. But what you don’t want to do is wish stresses away to get your design to the next milestone … that never ends well.

Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches.

Show Notes

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