T-Cell Thermal Battery Dummy

In the development of batteries for vehicle drives, thermodynamics, or thermal management, has recently come to the fore. This is due to the fact that the usual lithium-ion cells have to be operated within a narrow temperature window and because a lot of heat is generated, especially during so-called fast charging. The charging time, which is so important, is therefore directly dependent on the performance of the cooling system.

The experimental study of lithium-ion batteries is difficult because one is tied to the electrochemical processes, although they are not directly relevant to cooling studies. In addition, Li-ion batteries are extremely uncomfortable in the event of a fire, which requires significant safety precautions.

The aim of the T-Cell project is the development of a thermal dummy ('thermal cell') of a Li-ion cell, in which the heat generated by heating elements is simulated. Such a dummy allows experimental investigations on battery cooling to be carried out in a controllable, reproducible and safe manner. The focus of the project is on the application at module level, i.e. the combination of several cells.

A thermal cell enables studies of heat dissipation on the cell housing. Thus, innovative cooling concepts at cell level and module level could be examined.

This project is carried out in cooperation with the Institute for Electrical Measurement Technology and Sensor Technology and is funded by the Austrian Research Promotion Agency (FFG) as part of the "Mobility of the Future" program.

Halfway through this one-year project, a first prototype is available that has exceeded the original expectations. It has been possible to install power electronics that can be controlled from the outside inside the dummy. The communication action via a serial protocol is superimposed on the power supply. This means that only two electrical contacts are required for the dummy, which makes it possible to exactly replicate the external shape of a real cell. No additional lines are required for communication. Communication takes place via the U-ART protocol. The heating was designed as a copper winding that sits on an integrated coil former. This was produced using 3D printing and also serves as a carrier for the electronics and as an upper end cap. Due to a lack of availability, the outer shell had to be manufactured in-house. For this, 0.25 mm thick steel sheet was used, which was laser-welded.

Parallel to the development of the dummy, a compact, mobile and self-sufficient test setup was developed. It is used to carry out later experiments with the dummy, both at cell level and at module level. The experimental setup has its own control and data acquisition unit. In particular, the setup allows experiments with liquid cooling to be carried out.

The first measurements with the prototype have been completed. It could be shown that the dummy can reproduce the outside temperature of a real cell in a charging cycle with 3C. Thus, the dimensioning and controllability of the dummy is proven.

The other activities include the construction of the SiL environment, in which the heat generation of a real electrochemical cell is simulated, while the heat transfer to the outside is the result of the measurements with the dummy. This SiL environment is a central component of the planned measurement methodology. In addition, the electronics and the heating device are to be improved and further miniaturized in order to increase flexibility in the direction of other cell designs.