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Battery Systems

Battery systems considers the scaling from individual cells to battery packs, covering the connection, sensing, casing and tests for those solutions as well as the battery management. 

Different designs are considered depending on the objective of a battery system in terms of power, energy, or grid connection requirements.  

As important as the purpose of the battery are the chemistry used, which will have implications on allowable voltage, current, temperature and ageing for the facility.



Second-Life Batteries

Second-Life batteries means the reusing of cells obtained from mobile electric devices like cellphones, notebooks or automobiles.   

The task involves retrieving information about different cell types and their operational history, designing tests that can determine their state of health and correlate them to the service life that these cells can have in a second use. Conditions on a second use must carefully selected to allow a use according to the degradation of those used cells, and performance must be tested to prove their lifetime and compare their condition to new cells. At the end, being able to relate information on the history, current state of health, and performance in a second life will determine if the cost of these used cells can be lower than using new batteries.

Hybrid Energy Storage Systems


Energy storage system hybridization is characterized by beneficial combination of two or more energy storage technologies with supplementary operating characteristics such as energy and power density, self-discharge rate, cycle efficiency, life-time, set-up cost, etc. The hypothesis is such that the total energy throughput of a storage device is much reduced and the thermal stresses caused by high discharge rate responses are mitigated.

Defining the best size and structure for hybrid energy systems (HESS) requires a deep understanding of all its components. To acquire the knowledge involves building an actual prototype of the system and testing all the possible configurations. As a result, a computational model is required. Running multiple simulations in order to study the impacts and compare relevant results.


HESS is typically coupled with power converters through DC or AC network. Different converters exist. The choice is dependent on the applications. Power converters are used to control the power flow among the different storage elements. There are different ways of coupling different batteries using power converters. There are both series and parallel converter arrangements. Depending on the complexity of the control strategies, the use of power converters and microcontrollers can be expensive. Hence, the trade-off between economic feasibility and technical advantages is crucial in determining its financial and technical viability and implementation.

One major challenge in a Hybrid Energy Storage Systems (HESS) is the design of the energy management controllers for real-time implementation to yield a good power split performance. An imbalance often develops between the dc link bus and the battery bank voltage as a result of the battery change in SOC. This change occurs even when the battery voltage sizing were initially careful determined. A fixed structure of an HESS bank seems insufficient to solve this issue. Although, a run time reconfiguration of the energy storage banks has been proposed in the past, its comparative study in terms of energy efficiency, capacity utilization, scalability, flexibility, hot swap capability, cost as well as the overall systems enhancement is yet to be established. Other critical areas in the study of HESS include charge allocation, charge replacement and charge migration within the energy storage systems.

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Technische Universit├Ąt Berlin
Electrical Energy Storage Technology
Institute of Energy and Automation Technology
Faculty IV
sec. EMH 2
Einsteinufer 11
D-10587 Berlin


Sec. EMH2
Room EMH 162
+49 (0)30 314-21633
+49 (0)30 314-21133