Batteries for electric vehicles (EVs) have a limited lifespan that varies depending on the format, chemistry and manufacturer. After this time, used automotive battery packs are sent back to the manufacturer for disposal and recycling. 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.

Challenge

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. Although this market is very new, Francisco Carranza, Managing Director of Nissan Energy, sees it as a natural extension of what Nissan already does.

“Once you start selling electric cars there are a number of implications,” he reflects. “It’s important that we take care to develop products and solutions that help EVs be integrated into the electricity grid, so that they don’t create unexpected problems like saturation of the grid. At Nissan, we believe in a world where solar and wind energy, combined with stationary storage and EVs are the backbone of sustainable mobility.”

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. In anticipation of rising demand, and to evaluate the feasibility of this emerging business opportunity, the challenge was set to demonstrate 1MWh of energy storage at Nissan’s second-life facility in Sunderland by the end of 2019.

Francisco explains: “The key issue with second-life is that you need to have your costs under very tight control. This means having efficient processes that are as precise as possible in the minimum amount of time. Having a solution that allows us to grade in this way is fundamental to ensure the competitiveness of the final product.”

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).

Solution

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 team also trained and supported the Nissan Energy team in order to achieve the target of 1MWh of second-life energy storage.

Then, novel algorithms for grading battery modules were developed by WMG for use in specialist equipment supplied by AMETEK. This methodology reduced grading time from three hours to less than three minutes per module, with a proven accuracy of ±3.2% in State of Health (SOH).

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.”

Impact

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%.

Although Francisco says it is too early to say what financial impact all of this could have for Nissan, he emphasises the role of this project as an enabler for future investment in second-life. “It is very exciting,” he says. “It is going to contribute to a more circular economy, and help our customers to deploy solar and become more efficient. It’s really an environmental contributor and a social contributor.”

And it’s not just Nissan who are seizing the potential of second-life batteries. AMETEK have registered a patent for the integration of WMG’s grading algorithm into AMETEK machines. The new grading process and the methodology in the patent will be applicable to other OEM battery modules, demonstrating further valuable business opportunities for UK manufacturing.

For more information on this project, please see the UK-ESL Public Report here.