EV Battery Longevity

EV Battery Longevity

Posted by : Sarah Halliday   /  

This is part five of five in a series of blog posts to answer questions that were received via social media. For the next five days I will publish a new blog post every day relating to the following questions:

  1. How do EV’s and their batteries perform in cold temperatures?

  2. What are the cost differences between driving electric vs. gas, including maintenance and service costs?

  3. What is the current state of charging infrastructure in NL?

  4. What charging equipment do I need to charge at home?

  5. How long do the batteries last before they have to be replaced and at what cost?

Today I will be discussing the most important part of an electric vehicle: The batteries.

EV Battery

Batteries have been around for a long time and we are all very familiar with. Even new battery chemistries like lithium-ion have now become commonplace in all of our devices such as phones, tablets, computers, cameras, etc. Because of this we are all very familiar with the downsides of batteries. One of these downsides is battery degradation and longevity. It is very common to have to replace the batteries in say a five-year-old laptop or even the 12 volt battery in your typical ICE vehicle.

So what does this mean for batteries in electric vehicles?  The battery pack is by far the most expensive component in the entire vehicle. Depending on the size of the battery pack, its cost could range from $3,000 to $35,000 at todays prices. Current battery costs range from $300-$600 per kWh. Using the size of the battery, in kWh, you can figure out roughly the battery pack costs based on those prices.

Nissan Leaf Battery Pack (24 kWh)

Will EV drivers have to worry about replacing the batteries after three or five or even seven years? The answer is no, but they may have to replace the batteries after eight years. However, I will explain later why that should not be an issue.

The most important thing to know about the batteries longevity is how long they will be covered under warranty. Electric vehicle manufacturers want consumers to feel good about purchasing such expensive batteries so the industry standard has become an eight year, 100,000 mile warranty. In fact, some manufacturers are offering eight year, unlimited mile warranties. This means that if there’s any damage done to the battery or if there is significant range loss to the battery degradation during this period, it will be covered under warranty.

Tesla Model S Battery Pack (85 kWh)

The reason why they’re able to provide such an incredible warranty is because they are so confident in the technology that they implement in their battery management systems. These batteries and battery management systems have been put through rigorous testing in all types of conditions to ensure they operate as designed for as long as possible. The result of which is a large reduction in battery degradation overtime. They have not reduced it to zero but they have significantly slowed it to the point that they are confident in an eight-year lifetime of the battery.

Check out this graph which shows the results of a battery degradation survey of Tesla Model S owners. As you can see the battery degradation has been very small and is likely to continue the trend.

Tesla Model S Owners Battery Degradation Survey

So what happens after eight years and the warranty is up? Then depending on how much range is lost through battery degradation you may wish or may not wish to replace the batteries. What I mean by that is after eight years you may find the battery range is still largely available and still meeting your driving needs. For example, if your initial range was 160 km and after eight years you still have 80% available you may think 128 km is still enough for your daily driving and do not need to replace the battery. Or if your initial range was 425 km and you still have 340 km available to you might want to hold off on replacing your battery a little longer. I used to 80% remaining battery range, as it is the unofficial definition of “significant” battery degradation over 8 years. That is 20% degradation over 8 years or 2.5% per year.

If however, after 8 years you feel the battery degradation is too much and the vehicle has lost too much of its initial range, or if the battery gets damaged for whatever reason you can purchase a new battery. What’s important though is the pace of battery technology improvements and cost reduction. If you look back at the price of battery technology over the years there have been tremendous reductions. Check out this graph below.

Chart

This means that to replace the battery in an 8-year-old vehicle may be only half the cost that it is today. Furthermore, when you go to “trade-in” your old battery pack for a new one you will get a credit for your old battery as it will likely be repurposed for a different application. This would bring down the cost of the new battery even further. 

Another possible outcome is that if there are any individual batteries in your battery pack that have degraded more than others, those individuals cells may be able to be repaired or replaced eliminating purchasing a new battery all together.

The bottom line is that battery replacement costs and lifetimes is not something that people have to be concerned with today. They should feel confident in the 8 year warranties that come with the vehicles and should be aware that if the batteries need to be replaced after that time there will certainly be cheaper alternatives than purchasing a battery at today’s prices. 

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