All About EV Batteries
Let's answer a couple of really important questions about EV batteries. Mainly, how long will they last, and how much will it cost to replace them?
Battery Longevity: How Long Do EV Batteries Last?
Most people have very limited knowledge or experience when it comes to rechargeable batteries. We just don't have very many devices in our lives that use them. So, naturally, what's the first thing that comes to your mind? Well, for most of us, it's our smartphone. We use them all day long and then plug it in nearly every night. And in 2 to 3 years our phones don't hold a charge for the entire day and it's time to replace the battery. With this in mind, it's only natural to assume that the rechargeable batteries in EV's would follow a similar pattern, right? Well... no. In short, EV batteries are often designed to be used for a decade or more before being recycled or repurposed for use in another application. Let's look at how that works:
Battery Thermal Management
There are two main factors that affect the longevity of an EV battery, temperature, and charging cycles. Out in the real world, nothing will adversely affect a battery more than extreme temperatures. Lithium-ion batteries operate best and last the longest in temperatures close to 70 degrees Fahrenheit (about 21 degrees Celsius). Many EV drivers notice decreased charging performance if the temperature drops too low, usually below freezing, but nothing will kill a battery faster than prolonged extreme heat. Managing the thermal condition of a battery is the most important way to protect it from accelerated degradation. Most EV manufacturers use an Active Thermal Management systems for their battery packs that allow a liquid glycol mixture (coolant/anti-freeze) to flow through and remove heat from the battery pack. That's why on many EVs you will still have a coolant system and radiator. This is a big deal, especially for owners who live in very hot climates like the southwest United States. The Nissan Leaf is an EV notorious for not having active thermal management and many owners in hot regions noticed severe battery degradation. Before buying a used EV, it's a good idea to check the health of the battery. We get into that a little bit in our Are used EVs a good option? page.
Charging and discharging, the battery cycle
The other significant factor that affects longevity in Lithium-ion batteries is how we use them.
Thinking about our cell phones again, they are designed to start their work day at full capacity, and in order for us to be able to use our phones all day, the cell phone manufacturers give us access to use all of the energy in the battery. We start at 100%, and can deplete nearly all of the energy available in the battery as the day goes on. However, when we run the batteries all the way down to zero or close to zero, and then charge it back to 100%, it's very hard on the battery. Over time, the performance of the battery degrades. This has been accepted as normal usage for these devices, but it also means that within a few short years, we've degraded our batteries to the point where we often will need to replace them... or buy a new phone entirely. That's bad news for phones.
However, the good news for electric vehicles is we typically don't have the same charge cycle patterns. One, we don't usually use all of the available energy in the battery on a daily basis, and two EV manufacturers have built buffers into how much of the battery is available for use. Not all, but many EV manufacturers don't let the battery deplete all the way to 0% or let the owner charge all the way to 100% either. They do this to prevent severe battery degradation and increase battery longevity.
Don't worry about it
No battery is a perfect battery and EV manufacturers recognize this. However, they are very confident in the longevity protections they have put in place and, as an added assurance to owners, provide a warranty on the battery and charging systems. Many such warranties can be as much as 8yrs and 100,000mi! These long warranties certainly wouldn't be offered by manufacturers if they had any reason to suspect that the battery would fail within this time frame. Even so, the batteries are designed to last much longer with some of the latest battery technology talking about having an operational life of 1,000,000mi. Yeah, you read that right... 1 million miles.
How much does it cost to replace the battery in an EV?
The price of Lithium-ion batteries has fallen significantly as more and more are being made and manufacturers are researching more efficient and cost-effective ways to make them. Ten years ago, the cost per kWh of a Lithium-ion battery pack was as much as $1000. These days costs are much less and most EV manufacturers are chasing a price just 10% of that. They're not quite there, but they're getting close.
So there you have it, chances are you will never have to worry about replacing the battery pack in an EV if you're buying new. And if you happen to have an older EV, replacing the battery pack isn't nearly as expensive as replacing the vehicle itself.