Large battery packs used in electric vehicles (EVs) are more robust than laptop batteries, but like other lithium-ion batteries, they deteriorate over time. Here, we will look at the causes and reasons for the deterioration of EV batteries.
Related: How do electric cars work?
How EV batteries deteriorate over time
There are two main factors that affect the speed at which an EV battery deteriorates. Battery age, and usage and environment. The second category includes how to drive an electric vehicle, how to charge a battery, how to store a vehicle, environmental factors such as climate.
The first category, battery aging, is inevitable. All lithium-ion batteries are steadily less effective with use. This, also known as calendar aging, is a very step-by-step process. Also, it does not occur at the same rate as the previous year.
According to electric vehicle startup Recurrent, which monitors used electric vehicle reports and provides them to shoppers, EV batteries show a maximum reduction in capacity at the beginning and end of their usable life. It usually drops rapidly at first. This will level off once the battery stabilizes and will drop further after a few years. These reductions are usually modest and are between 5-10% of total capacity even after thousands of miles.
So why does this deterioration occur? The cause is how the lithium-ion battery is manufactured and operated. Electric vehicle batteries rely on chemical reactions to generate the electrons that power the vehicle’s motors. They produce them by using so-called “active substances” to provoke reactions. For lithium-ion batteries, the material is lithium.
Since the battery is used many times, some of its lithium is used up forever. If that happens long enough, there is not enough active material to produce the same amount of energy, reducing the overall charge that the battery can hold. This type of degradation is also known as capacity fade.
Environment and usage factors
Environmental factors, especially temperature, have been shown to affect the operation of EV batteries. For example, in very cold weather, the liquid in the battery of an electric vehicle becomes more viscous, slowing down the reaction required to generate electricity. This means that the motor can use less power and therefore less power to accelerate. This is, of course, called a power fade. EVs are built using temperature control systems to prevent this, but extreme weather causes some problems. Power can also be reduced if the inside of the battery corrodes or accumulates over time.
And it’s not just cold. Heat can temporarily reduce capacity and contribute to accelerating overall capacity loss, but in modern EVs the difference in capacity lost between warm and hot climates is small. As Cars.com says:
“Four years later, EVs in warm climates have less battery degradation than EVs in hot climates, but the difference is less than a quarter percent … without active thermal management 2015, according to Geotab data. A comparison of EVs for the year model, the Nissan Leaf, another 2015 Tesla Model S with it could be most useful. Geotab has an average leaf shrinkage rate of 4.2% and a Model S of 2.3%. I am reporting. “
Great reliance on direct current (DCFC) stations also reduces EV battery life. Automaker Kia believes that a 10% capacity loss over the entire battery life is due to overuse of DCFC. DCFC puts a heavy load on the battery pack to quickly turn on all the power. This is the same as always using fast charging on your mobile phone will shorten battery life. This is because the more power you put into the battery, the more powerful the electrons and ions move inside the battery cell. This can cause minor damage and extra stress on the battery components and, if done frequently, can reduce capacity.
Most electric vehicle manufacturers agree that fast charging should be used “modestly”, but at the time of this writing, there is no clear definition of conservative meaning. If unavoidable or on long trips, it is advisable not to charge as fast as possible and in most cases maintain normal level 1 or 2 charging.
Do you need to worry about battery deterioration?
As long as you realize that the battery capacity will gradually decrease, you don’t have to worry too much about deterioration over time. However, you need to plan the reduction in advance and take that into account in the calculation of the distance you can drive the vehicle in the next few years. As far as a complete failure is concerned, the failure of the entire battery is very rare and is usually covered by the manufacturer’s warranty.
Some deterioration is unavoidable, but with careful battery care, most of that range can be sufficient for the life of the car. Make sure the DCFC is not overcharged. Pre-adjust the battery to extremely hot or cold temperatures before charging. If you can save power, leave the vehicle connected to the charger. Before you buy, consider the climate you live in and how it affects your battery. As technology advances, many of these constraints on EV battery power and life can be mitigated or completely eliminated. This is especially good news if you know the cost of replacing an EV battery.
Related: How much does it cost to replace an electric vehicle battery?