Repurposing EV Batteries: Underwriters Laboratories Interview

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Underwriters Laboratories is developing a common set of requirements for evaluating and testing re-purposed EV batteries in order to reduce safety risks. Its UL1974 standard may be ready by the end of this year. Ken Boyce, UL’s Principal Engineer Director of Energy & Power Technologies, answered some questions on this topic for CleanTechnica.

used EV batteries stationary storage

How do you identify batteries at risk of thermal runaway?

UL spent the last 10 years researching batteries for ways to better understand evolving and emerging technologies. Our work with the National Transportation Safety Board in its investigation into the Boeing 787 airplane incidents led us to develop and publish a white paper on the causes of safety risks associated with lithium-ion batteries and applicable product testing protocols.

Currently, UL researchers and engineers are leveraging and extending those findings to develop proactive methods to identify batteries at risk of thermal runaway, especially when undergoing a second-life scenario. We are developing a standard to agree on those protocols that make us feel comfortable about repurposing products, especially vehicles, which use this technology.

How many EV batteries might find a second life in the next 5–10 years?

UL does not aggregate statistics on the future of the EV market. We know the number of EVs on the world’s road have been increasing to about 1.5 million today, and as the EV population ages we will see increasing availability of EV batteries for second life uses.

Will there be a market where EV owners sell them directly to people who will use them for stationary storage? Will EV owners be able to re-purpose their own EV batteries for home energy storage systems?

We are creating a standard for second-life EV batteries as we do believe there will be a market for this application. First, however, we would like to create a thorough, rigorous assessment before EV batteries are put into a new application, in order to help address potential safety risks. We are hoping to do so through a new, UL Standard (UL 1974) for second-life batteries looking at associated safety challenges.

Is there currently much awareness about how much a flood of used EV batteries could impact energy storage?

We don’t have any data on how used EV batteries may impact energy storage — however, we all want safe infrastructure. We hope EV batteries find their proper places in the market — UL’s role is to support ways in which to do that safely.

Can batteries in hybrid vehicles like the Toyota Prius also be re-used for stationary storage?

Yes. Whether it’s a hybrid or battery electric vehicle, in theory, all kinds of batteries could be used for stationary storage.

How much testing might be required to certify that a used EV battery is safe for use in stationary storage?

UL will do some upfront qualification test to assess the safety of the battery design. Then, we will focus on the protocols at the repurposing location as part of a follow-up service to help ensure the repurposing of the battery is done appropriately. Finally, we plan to provide some on-going testing of the products that are a result of that process.

Once a used EV battery has been tested and is ready for its second life, how long could it last in a stationary storage role?

Batteries undergo a life-cycle, much like a living thing. Their individual state-of-health directly corresponds to different environmental and usage conditions. So, we’re looking at the battery in terms of how it is used. UL conducts a rigorous assessment to minimize the risk that a hazard will emerge over that lifetime.

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