Ralf Benger

Technische Universität Clausthal | TUC · Research Center Energy Storage Technologies

A possible contamination with impurities or material weak points generated in cell production of lithium-ion batteries increases the risk of spontaneous internal short circuits (ISC). An ISC can lead to a sudden thermal runaway (TR) of the cell, thereby making these faults especially dangerous. Evaluation regarding the criticality of an ISC, the de...

The electrical energy system has to manage an increasing share of renewable energy sources while conventional power plants will be shut down soon. New technologies are necessary to secure the ancillary services and offer flexibility. Battery energy storage systems (BESS) can react very fast, they are a good option to support power system stability....

In recent years, research on lithium–ion (Li-ion) battery safety and fault detection has become an important topic, providing a broad range of methods for evaluating the cell state based on voltage and temperature measurements. However, other measurement quantities and close-to-application test setups have only been sparsely considered, and there h...

Identifying battery storage systems to ensure stable grid operation  The design of a correctly dimensioned battery storage system to ensure stable grid operation requires a holistic view of the entire system with regard to the storage unit, the inverter and the feedback of dynamic grid requirements.

With this paper a method to detect faults of lithium-ion cells during operation is first presented and later validated by experiment. Since every cell fault will increase the cell temperature towards its process until thermal runaway the method uses the temperature-dependent change of the cell impedance as fault feature. Using a 46 Ah pouch cell th...

A 46Ah cell was characterised by Electrochemical Impedance Spectroscopy (EIS) for parameterisation of a R-RC-RC equivalent circuit model. Samples were measured for all combinations of temperature (0, 10, 20, 30, 40°C) and state of charge (0, 10, 20, …, 90, 100%). The raw data was analysed by the Matlab extension DRTools to identify the most dominan...

The Incremental Capacity Analysis (ICA) uses the voltage characteristic as raw data and is considered as one of the most advanced non-destructive techniques for battery characterization. For the successful application of this method not only the parameters of the data recording are essential, but also the correct data preparation by filters is very...

The frequency stability in the electrical supply system is challenged by increasing inertia-free power electronics-based generation capacities. To mitigate this effect, high performance battery converter systems controlled as virtual synchronous generators can provide synthetic inertia. This paper presents a system design and a detailed evaluation...

Stable security of energy supply requires an equilibrium of supplied and consumed power at any time. Deviations between demand and supply cause an instant increase or decrease of the grids frequency. Ancillary services ensure a constant frequency in the public transmission grid by providing inertia and balancing power in form of primary and seconda...

A closer look at the current loads of electrical energy storage devices in converter-fed DC intermediate circuits reveals that in many systems they must be regarded as an AC or mixed current component and not as a DC component. This has significant effects on the current-voltage behaviour, the thermal behaviour and thus also on the lifetime of ener...

Durch die Transformation des Energiesystems und die flächendeckende Einführung von Elektrofahrzeugen entstehen neue Herausforderungen und Chancen für den Betrieb der Stromnetze mit zusätzlichen Lasten und für den vertriebsorientierten Handel an den Strommärkten. In dieser Hinsicht sind Berührungspunkte zwischen der Branche der Energiewirtschaft und...

Fuel cells consist of single cells that are connected in series to form a stack. This increases output voltage and therefore decreases current-dependent power losses, but the electric current of the stack has to flow through each single cell. In case of an increase of resistance or a failure of just one single cell the whole stack is affected. The...

To build a lithium battery system from single cells for use in an electric drive system the coupled electrochemical and thermal characteristics of these cells have to be well-known. Otherwise it is not possible to find the best cell for a given application considering capacity, power, thermal and electric management, housing, monitoring, etc. In th...

A method to characterize an electrochemical system like a battery for HEV or EV application is the measurement of the internal resistance. In the literature many different approaches to determine the parameters of a battery are described. The standard methods to diagnose the state of health of a battery system are typically based on tests with smal...

A simulation programme for the power supply system of a train makes it possible to select the technically most suitable and most cost efficient battery for an application. The program calculates the voltage and temperature behaviour of batteries in rail vehicles. It is also possible to estimate the lifetime and costs of batteries in the application...