In the coming year, batteries in the first wave of electric vehicles (EVs) will come to the end of their warranties.
Car manufacturers, working with universities and other partners, have been deploying out-of-warranty EV batteries for stationary storage projects, as batteries can still retain up to 80% of their storage capacity.
UL is developing a common set of requirements for evaluating and testing re-purposed EV batteries, for the so-called second-life EV battery market.
The requirements aim to reduce potential safety risks and provide the industry with standards to adhere to for testing former EV batteries.
A second-life EV battery market allows redeployment of lithium-ion and other EV batteries instead of disposing of them and can potentially reduce the cost of EVs if there is a viable market for out-of-warranty batteries.
Redeploying used EV batteries could also potentially halve the cost of stationary storage.
About 95GWh of lithium ion batteries are expected to come out of cars by 2025, compared with about 0.1GWh of used electric car batteries available today. Around 26GWh of this capacity will be converted to stationary energy storage systems, according to Bloomberg New Energy Finance.
Until now, the industry has lacked a uniform set of standards governing how former EV batteries intended for stationary storage applications are tested.
UL expects its UL1974 standard to be ready by the first quarter of 2017. The standard sets out common requirements for the assessment of batteries intended for second life stationary storage applications, whether in a utility-scale storage systems, a microgrid or in behind-the-meter residential applications.
Testing approaches
Some of the basic scientific principles will cut across all applications.
"There will be some common requirements regardless of the final end-use stationary storage application," said UL's principal engineer director for energy and power technologies, Ken Boyce.
"As the requirements are finalised, there is the opportunity to customise requirements to ensure that the process reflects the unique different usages and addresses the needs of the users in the varied applications," Boyce added.
UL has, in the past, developed safety standards for batteries and battery-powered equipment. This requires testing representative samples before they enter the marketplace and also providing regular surveillance of manufacturing at the production facilities.
Out-of-warranty EV batteries require a different procedure. The strategy UL is finalising will include both complete testing of representative samples to all test requirements, including destructive tests, and then comprehensive, non-destructive assessments of each repurposed battery.
"Some approaches test the battery at pack level, while other companies that are repurposing these batteries are going into the pack to test at the cell level, so our standards have to accommodate both of these main approaches," explained Boyce.
The company started writing the standard earlier in 2016. However the groundwork — involving collaborating with automotive companies, battery reclamation and reconditioning companies as well as utilities — has been occurring for several years.
