A report, commissioned by the Office for Product Safety and Standards (OPSS), entitled ‘Safety of Second-life Batteries in Battery Energy Storage System’, and prepared by P. A. Christensen (who spoke about this subject at the ATF Professional conference in 2022), W. Mrozik and M. S. Wise, School of Engineering, Newcastle University, was published this week at gov.uk.
The report provides an overview of the market for second-life batteries. It reviews the hazards for lithium-ion batteries and the risks specific to second-life batteries, including batteries from electric vehicles, with a description of gateway testing and other mitigating measures. It also provides a detailed analysis of the relevant codes, standards and regulations, and considers best practice when using second-life batteries in battery energy storage systems (BESS). Input to create the report was gathered from representatives from over 30 organisations, including BESS and electric vehicle manufacturers and suppliers, industry associations, battery recyclers, research institutes, public and government bodies, product safety experts, and standards bodies.
Electrical energy storage will be a critical source of flexibility needed to transform and decarbonise the energy system. These systems allow for the storage of energy for times when it is needed and increase the flexibility of the grid, which is key for integrating variable renewable generation. From a consumer perspective, domestic lithium-ion battery energy storage systems (DLiBESS) are becoming an attractive option, particularly when installed alongside onsite generation such as solar photovoltaic (PV), enabling the consumer to maximise the use of this generation and to buy and sell electricity at times that are financially advantageous. This is particularly beneficial when used in conjunction with Demand Side Response (DSR).
Although few incidents of thermal runaway with DLiBESS are known in the public domain, such an event could present hazards such as fire, toxic gas release or explosion. The report addresses the use of second-life lithium-ion batteries in DLiBESS driven by the significant increase in the availability of second-life electric vehicle (EV) batteries resulting from the global drive to decarbonisation.
However, there is a concern that second-life LiBs may have a greater risk of failure if steps are not taken to adequately mitigate this risk. Therefore, the aim of this study is to improve the evidence base available to OPSS on the safety risks and hazards associated with the application of second-life lithium-ion batteries in domestic LiBESS and measures to mitigate these, including an assessment of best practice and standards.
Extensive discussions with stakeholders have revealed two opposing views on second-life batteries: firstly, that a safety framework can be put in place to allow the use of second-life LiBs in DLiBESS, so long as the full history of the batteries in their first life applications is known and/or they can be tested effectively. A second, more radical view shared by some respondents is simply that the safety of such cells can never be guaranteed, and hence that second-life LiBs should not be employed under any circumstances in DLiBESS.
Lastly, due to the fire and electrical hazards associated with LiBs, the availability of potentially untested second-life LiBs and the potential lack of knowledge (for example, with LiB ageing) and skills of consumers to mitigate the risk through testing and good system design, consideration should also be given to whether stricter requirements are needed for home-built (“DIY”) DLiBESS that use second-life batteries.
Professor Paul Christensen, Newcastle University, commented:
“Without a shadow of a doubt, the recycling industry is crucial to the success of the drive to decarbonisation through the electrification of transport. However, the very high energy densities of lithium-ion batteries and very large volumes of toxic and explosive gases released when they enter thermal runaway demand detailed training for their handling and a highly responsible industry.”
To read the full report, go to assets.publishing.service.gov.uk/government/safety-of-second-life-batteries-in-bess.pdf