Adaptive Battery Fast Charging (ABSL)

The ongoing conversion of large areas of private transport from fuel-powered to battery electric vehicles (BEVs), which is being pursued as part of the mobility transition, is making only slow progress, particularly in Germany. The low level of acceptance of electric cars, which is the cause of this, is primarily due to the comparatively higher purchase cost, shorter range, the unavailability of charging infrastructure and the duration of the charging process, which is perceived as inconvenient. Since the prices for Li-ion cells have already fallen sharply and considerable progress seems achievable in the charging infrastructure, the problem of low range in conjunction with long charging times is increasingly predominant. In this context, the well known increased aging of batteries due to high charging power is of great importance, because short charging times can only be achieved through high charging power.

The established standard technology for BEVs is the lithium-ion accumulator (LIA). When used in vehicles, a large number of individual cells are connected in series to achieve the voltage of typically several hundred volts required in the vehicle. Since the individual cells have different capacities due to manufacturing tolerances or different cell temperatures, for example, and react sensitively to overcharging or deep discharge, a battery management system (BMS) must be used to monitor the individual cells and, if necessary, the state of charge of the individual cells must always be equalized by taking suitable measures.

The core element of the combined feed-forward and feed-back control of the charging current of the cell is a diagnostic method to be developed, which uses the means available in the BMS to determine the state of health (SOH) of the cell to be charged. If this aging progresses faster than defined by a default value, the charging current is reduced by a charging current controller. If, on the other hand, the current aging is slower than tolerable, the charging current is increased and thus faster charging is realized. To reduce the load on the controller, a feedforward control (inverse SOH model) is also developed, which determines a maximum charging current based on the currently present boundary conditions (e.g. cell temperature, state of charge, etc.).