December 5, 2015

Electric cars: batteries with brains

Intelligent cell of the Fraunhofer IPA: A microcontroller records physical parameters
such as temperature and state of charge. If a cell is empty, it switches itself off automatically.
© Fraunhofer IPA

(December 5, 2015)  The battery is the heart of the electric car. Fraunhofer researchers have developed an energy storage device which is significantly more cost-effective over the entire life cycle in comparison with previous models. If one of the more than one hundred battery cells is defective, it can be replaced easily. Until now, the entire battery had to be replaced.

The core of electric cars are their batteries. So far, these have been monolithic blocks in which the individual battery cells as well as the necessary technology have been housed. All individual cells should theoretically be able to save the same amount of energy. In practice, though, this is somewhat different: due to production reasons, their capacities vary. This is problematic, since the cells are connected in series. The entire battery is therefore only as strong as its weakest cell. If this cell is “empty”, the remaining energy in the other battery cells does not help – the car has to be recharged. For that reason, manufacturers presort and install cells of a similar capacity into a battery. Since some cells are sorted out as a result of this process, and this pushes the price of the batteries up. Another shortcoming is that when a cell is defective, the vehicle stops functioning. That means that the entire energy storage device has to be replaced.

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