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Rapid grading for second-life automotive batteries

Rapid grading for second-life automotive batteries


Batteries for electric vehicles (EVs) have a limited lifespan that varies depending on the format, chemistry and manufacturer. WMG’s battery technology experts in the Energy Innovation Centre developed a safe, robust and fast methodology for grading used automotive Lithium-ion batteries.

The pack and module grading methodologies developed in this project have opened the door for Nissan to grasp the opportunities offered by second-life.

Used automotive battery packs are sent back to the manufacturer for disposal and recycling after their limited lifespan. However, used Lithium-ion batteries often retain sufficient energy and power capability and might be suitable for ‘second-life’ applications, such as in renewables and static energy storage for domestic and industrial use. Manufacturers and reprocessing centres are under pressure to come up with robust grading processes to evaluate the economic liability of repurposing used Li-ion batteries, instead of disposal and recycling.

Following high sales of the Nissan LEAF since its European launch in 2010, Nissan have been keen to explore the second-life Lithium-ion battery market as an opportunity to create a new income stream and extend the battery value chain.

Currently, the number of battery packs being returned to Nissan is very low, just tens per year. But from 2021, when the first vehicles start reaching the end of their life, those numbers will start ramping up. With no commercially available solution that met their requirements, Nissan partnered with WMG, AMETEK and Element Energy on the “UK Energy Storage Laboratory” project. Funded by the Department for Business, Energy and Industrial Strategy (BEIS).

To meet this industry challenge, WMG’s battery technology experts in the Energy Innovation Centre developed a safe, robust and fast methodology for grading used automotive Lithium-ion batteries, initially, at pack level. This methodology was successfully transferred to the Nissan second-life facility.

Our Approach

Speaking about the approach we took to this project, Professor Dave Greenwood, Professor of Advanced Propulsion Systems at WMG, said: “To significantly increase the speed of module and pack testing meant moving away from traditional methods which simply charge and discharge the battery to see how much capacity it has left in it. In this project we brought testing techniques which are usually only used in laboratory environments into an industrial context. These much faster techniques measure the electrochemical performance of the materials in the pack, and our scientists were able to develop algorithms which accurately relate those characteristics to the remaining useful power and capacity of the used battery pack.”

The pack and module grading methodologies developed in this project have opened the door for Nissan to grasp the opportunities offered by second-life. It is the first time that the pack grading methodology has been demonstrated for volume manufacturing outside of the laboratory environment, showing its potential as an industrial system, able to scale up quickly to handle the volumes expected after 2021.

The process for grading battery modules is now being trialled at the second-life pilot facility. Nissan hopes to be able to re-use 90% of battery packs currently assembled in EVs in Europe by 2021, and has a plan to recover and recycle the remaining 10%.