An electric vehicle battery degrades just like any other battery. In practice, this means that the capacity of the battery and thus the range of the vehicle degrades. On average, a battery loses 2.3% of its capacity every year.
This is according to figures from fleet telematics company Geotab. Battery degradation is a natural process in which the amount of energy that can be stored or the amount of energy that can be delivered is permanently reduced.
"Batteries in electric vehicles can generally deliver more power than drivetrain components can handle. As a result, power degradation is rarely noticeable in electric vehicles and only the loss of power to store energy matters," writes Charlotte Argue, Senior Management Fleet Electrification at Geotab, in a blog post.
Several factors influence
All kinds of factors affect battery degradation. These include time and temperature, but also the number of charging cycles. In addition, using the battery while it is high or low in energy can also have an impact. Although much research has been done on battery life, relatively little data is available on their performance in practice.
Geodata therefore examined data from 6,300 vehicles - owned by both businesses and consumers - to map the real-world performance of batteries. The data shows that batteries lose an average of 2.3% of their capacity per year, which is less than expected. Geotab states that, in many cases, battery life exceeds vehicle life.
Lifespan cannot be predicted
However, exactly how long this lifespan is, the company does not dare to predict. Among the batteries surveyed, Geotab says there are very few that have reached the end of their lifespan. Degradation of batteries is non-linear. At the beginning of its service life, the battery degrades relatively quickly. After this phase, the capacity continues to decline, but the rate at which this happens flattens out. Towards the end of its service life, degradation accelerates.
Geotab points out that many car manufacturers offer a warranty on the battery. In many cases, it is guaranteed for the first 160,000 kilometres or eight years. However, this varies by manufacturer and country. Geotab also points out that the price of batteries is falling rapidly. For example, the average price of lithium-ion batteries has fallen by 80% since 2010.
Compare car models
To analyse the data, Geodata has developed a tool called 'EV Battery Degradation Tool'. It is available on the company's website and allows mapping the performance of batteries in specific car models. Among other things, the tool shows that the passive air cooling of a 2015 Nissan Leaf - designed to cool the battery and prevent degradation - performs less well than the liquid cooling in a Tesla Model S of the same year of manufacture. The Leaf shows an average battery degradation of 4.2%, compared to 2.3% in the Tesla.
More information can be found in the blog post published by Charlotte Argue about the study.
Author: Wouter Hoeffnagel
