Li-ion batteries can still be useful as low-cost energy storage after their first use in electric vehicles.The research project LibforSecUse aims to develop secure procedures and supporting metrological infrastructures to measure Li-ion batteries residual capacity.Such procedures are needed to test if it is economically and ecologically reasonable to use large numbers of used Li-ion batteries as energy storage.As partner in The European metrology research project "LibforSecUse" the Joint Research Centre (JRC) will take part in a workshop organised by the