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F. Demmelbauer-Ebner:
"Technical evaluation of business opportunities for battery second lif e usage of electric vehicles";
Supervisor: P. Hofmann, D. Geringer; Institut für Fahrzeugantriebe und Automobiltechnik(IFA), 2020; final examination: 2020-09-14.

Due to increasing environmental awareness and resulting legislative changes regarding CO2 limits, motorized individual transportation is heading towards electrification using lithium-ion batteries to power electric vehicles. The built-in batteries offer eight to ten years guaranteed lifetime. After that time, batteries are considered inappropriate for further use in the electric vehicle, but still have a capacity of ~80%. Consequently, the batteries can be removed from the electric vehicle (EV) and put into different applications with milder operating conditions. This results in the emergence of a new market, which deals with battery second life solutions. This work gives an insight into battery second life usage considering both technical and economic aspects. Two perspectives are taken into consideration: Firstly, an OEM's point of view is investigated. Secondly, a customer's perspective is looked into. The OEM has battery know-how and the financial ability to scale up batteries for both - building a primary control reserve as well as recycling facilities. Nevertheless, the OEM needs to find a way to get access to spent EV batteries within a financially feasible scope, including buying and repurposing the batteries. On the other side, customers possibly want to continue using their battery after its end of life in the EV, but do not have the capabilities to repurpose the battery. Since batteries differ from each other, assumptions are made in order to represent the average spent EV battery in the future (referred to as BEVeq battery in the course of this work). lt is assumed that the average second life battery has a capacity of 80% and reaches its end-of-life at 60% of the initial state. Afterwards, typical load characteristics of the two application scenarios are applied into a battery aging model. At some point during the battery's second life, the aging behaviour of the battery starts to accelerate rapidly. Due to a lack of experimental proof or validation of data, most aging models do not take this non-linear aging characteristic into consideration, which results in high residual lifetimes. Furthermore, production inhomogeneities and the fact that each individual battery has experienced different loads over lifetime, lead to a large spread of second life aging behaviour. This results in various residual lifetimes, even for battery cells aged under the same conditions during second life operation. In this work, the residual lifetime of an average spent BEY battery is modelled using an existing aging model and scaling the original capacity decrease. Additionally, input parameters are varied as well, resulting in three residual lifetime scenarios for each application. In order to evaluate economic viability, the net present value (NPV) approach is applied to both use-cases and the recycling process. Assumptions are made in such a way that results target to give a long-term perspective on battery second life usage and recycling. Consequently, huge economies of scale are presumed, resulting in low battery repurposing and recycling costs. Finally, several influencing factors on the technological and economic feasibility of second life batteries are investigated and quantified. In this way it is not only shown what economic potentials can be found in the reuse and recycling of spent EV batteries, but also how certain market conditions affect the profitability of battery second use.