Researchers prolonging life-span of batteries in electric cars

Wednesday, May 9, 2018

The life-span of lithium-ion batteries is a limiting factor for the electrified cars of today. Researchers from Chalmers now have succeeded in developing models to avoid premature aging of batteries, models which can also provide the car with higher performance in terms of shorter charging time, longer mileage and faster acceleration. The research has been rewarded the Volvo Cars Technology Award.

Volvo Cars Technology Award

The researchers in the project were awarded the Volvo Cars Technology Award 2017. The awardees are, from the left in the picture, Doctoral student Anton Klintberg, Professor Torsten Wik, Hannes Kuusisto from Volvo Cars and Industrial doctoral student Björn Fridholm. They were all honoured with flowers and diplomas by representatives from Volvo Cars, with CEO Håkan Samuelsson in the lead.

​An increasing number of car owners consider replacing their fossil-fueled cars with vehicles that are powered entirely or partly by electricity. However, the batteries used in electric vehicles are still comparatively expensive, and there is still a lack of knowledge concerning how the battery life-span can be kept as long as possible.

”If you charge lithium-ion batteries correctly and use them in a smart way, you can avoid premature aging of the batteries,” says Torsten Wik, Professor and research group leader in automatic control at Chalmers. “It may sound simple but there are many factors to consider, and it is important to understand how battery life and function are affected.”

More precise and adaptive calculations
One of the difficulties is that it is not possible to measure the condition of the battery, it must be calculated. Also, the factors are constantly changing, depending on the temperature, current and cell voltage, as well as the age of the battery. This means that the algorithms must be adaptive in order to constantly adjust to the changing conditions.

“The novelty is that the algorithms we have developed constantly depend on the behaviour of the individual battery cells, instead of having to assess the condition of the battery in advance,” says Torsten Wik. “This makes our calculations much more accurate. The capacity of the battery is thus being used more efficiently, and you can avoid putting a strain on the battery that causes it to age prematurely.”

Tests show that the battery thus can deliver an additional 10 percent in peak power and that the actual maximum power can be estimated at an accuracy of 2 percent.

Lithium-ion batteries are central components in electric cars and have major impact on performance and costs for the future development of electrified vehicles.

The automotive industry shows great interest
Research has been ongoing since 2012 and is financed by the Swedish Energy Agency. Volvo Cars is participating as a partner, and Björn Fridholm, industrial doctoral student, has an active role in the project.

“The battery is the most expensive component in an electric car,” says Björn Fridholm. “If we can use the batteries more efficiently, it would be of great economic significance and a strategically important driving force for the continued development of electric vehicles. The cooperation with Chalmers has built up important knowledge, that we at Volvo Cars now are implementing in our products.”

Recently, the researchers in the project have been awarded the Volvo Cars Technology Award in the category Research. The project has so far resulted in three patent applications.

“It’s great that the results of the research have come to use so quickly,” Torsten Wik says. “Now we proceed to refine our calculation models even more. In the next step, we will focus on what is physically happening in the battery cells. This will require a large extent of computational power in the vehicle, but in return it is likely to provide additional potential of cost reductions and improved performance.

Text: Yvonne Jonsson
Photo: Volvo Cars