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Report RSE 17001214

Testing procedures and results of experimental activity on batteries of differenttechnologies and applications

A test procedure for the estimation of lifetime of energy storage systems and the final results of aging tests carried on three lithium-ion cells in different working conditions.

The estimation of the lifetime and ageing trend of a battery is very important during the planning phase of an energy storage system, in order to choose the technology suitable for a specific application, to optimize the size, design and management of the technology with the aim to calculate the economic value of the investment through a cost-benefit analysis. The battery lifetime estimation requires a great number of testing and modeling efforts to validate the results, because there are multiple stress factors that can accelerate battery aging and they can also act simultaneously.

The document describes a test procedure developed with the aim to analyse the aging of an electrochemical energy storage system. The procedure is not directed to evaluate the performances of a specific technology and is intended to be adaptable to accumulation systems of different sizes and characteristics.

The second part of the document reports the final results of an experimental activity started in 2014 with the aim to develop an algorithm for the SOC-SOH estimation of an accumulator based on its electrical model, able to adapt the estimations taking into account the changes of the electrical model parameters due to aging of the battery, in order to guarantee a good management of the energy storage system during its whole service life. The development of the algorithm used the results of an aging test activity, started in 2014 on three lithium-ion NMC cells, 3.7 V – 40 Ah each one, cycled in different working conditions.

The test results confirmed the temperature influence on cell aging rate and allowed to detect a relationship between the SOH trend of the cells and temperature. A proportional relationship between loss of capacity and number of work cycles has also been highlighted. The test results are described in detail in the document.

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