17 Dec 19

Telematics shows battery degradation is just 12% after 6 years

Geotab has developed a free tool to compare the average battery degradation over time for different vehicle makes and model years. The tool is based on an analysis of 6,300 fleet and consumer electric vehicles – both PHEVs and pure EVs. There are some noticeable differences between the models, but in general, battery degradation seems reassuringly limited. The free tool shows that on average, the State of Health (SoC) is still 87.9% after 6 years, meaning that just 12.1% of the initial kWh have been lost.

Battery degradation is a natural process that permanently reduces the amount of energy a battery can store, so after a few years your range will reduce. It depends on the age of the vehicle, on whether it is frequently used at high or at low state of charge (SoC), how many times the battery has been charged and discharged, and how many of the charging has been done by DC fast chargers.

Comparing models to optimise TCO

The interesting thing about Geotab’s research is that it provides real-life data from 21 different vehicle models, which have been followed during a total of 1.8 million days. It makes the data relatively representative and allows you to compare cars before you buy them.

In the Geotab blog, Charlotte Argue, Senior Manager, Fleet Electrification points at two reasons for the differences: battery chemistry and thermal management. Even though all batteries are lithium-ion, there is a difference in the materials used for the electrodes. Moreover, batteries with liquid cooling seem to perform better than air-cooled ones. As a case in point, the 2015 Tesla Model S lost just 2.3% on average, whereas the 2015 Nissan Leaf posted a 4.2% degradation.

The battery is an important element in the Total Cost of Ownership of an EV. The longer its health is sustained, the more range it gives and the less you have to recharge it – which is time-consuming. Also, the better the battery’s health, the higher the EV’s residual value. A 5-year-old electric car with a SoH of 90% will be worth more on the used-car market than a similar vehicle with just 75% left.

Non-linear degradation

Even though the graph shows a linear evolution of the battery’s state of health, it actually degrades non-linearly, Geotab has found. After an initial drop, the decline is quite linear, but towards the end of its life, the battery will see a final significant drop, as shown below.

“Fortunately for the drivers, too few batteries we’ve observed have reached the end-of-life drop for us to predict at what point this is likely to occur”, writes Charlotte Argue. “We will continue to monitor to see when the non-linear degradation (also known as the “heel”) begins.”

Discover what telematics can do for you

Global telematics company Geotab is founding partner of Fleet Europe's Connected Fleets Conference, the second edition of which takes place on January 28 and 29 in Brussels, Belgium. The theme of this conference is Parcel Delivery and Last Mile Solutions. You can discover the full programme and registration details here.

Authored by: Dieter Quartier