This paper presents an analytical time-domain-based parameter identification method for Thévenin-equivalent circuit-based lithium-ion battery models. The method is based on the analysis of voltage-relaxation characteristics of pulse discharge and pulse charge experiments, and the method can be used for both discharge and charge operation with any number of parallel resistor-capacitor branches. The use of the method is demonstrated for a second-order model and validated with a real-world duty cycle. Experimental results for a commercial lithium-ion battery module are presented.

The recent deployment of distributed battery units in prosumer premises offer new opportunities for providing aggregated flexibility services to both distribution system operators and balance responsible parties. The optimization problem presented in this paper is formulated with an objective of cost minimization which includes energy and battery degradation cost to provide flexibility services. A decomposed solution approach with the alternating direction method of multipliers (ADMM) is used instead of commonly adopted centralised optimization to reduce the computational burden and time, and then reduce scalability limitations. In this work we apply a modified version of ADMM that includes two new features with respect to the original algorithm: first, the primal variables are updated concurrently, which reduces significantly the computational cost when we have a large number of involved prosumers; second, it includes a regularization term named Proximal Jacobian (PJ) that ensures the stability of the solution. A case study is presented for optimal battery operation of 100 prosumer sites with real-life data. The proposed method finds a solution which is equivalent to the centralised optimization problem and is computed between 5 and 12 times faster. Thus, aggregators or large-scale energy communities can use this scalable algorithm to provide flexibility services.

This paper presents an electrical battery model for lithium-ion (Li-ion) batteries that can be used for dynamic simulations of hybrid electric non-road mobile machinery (NRMM) and other vehicles. Although the model has been developed mainly for large vehicle batteries with Li-ion based chemistries, it can be used for other battery chemistries as well. The parameters can be extracted from simple measurement sets. The model calculates e.g. state-of-charge, terminal voltage, and open-circuit voltage. In this paper, the model structure and parameter extraction are explained in detail, and a model for a 25.9 V lithium-ion polymer battery module with 40 Ah cells is presented. Parameters are extracted from experimental measurements and the model is validated by making another experiment with more realistic hybrid electric NRMM current profile.