*Further Work*

This article joins its solid foundation of referred literature, e.g., [13,15,16], that collectively doubt the influence of current ripple or alternating current on battery ageing. However, generalisation and transferability remain problematic as the vast amount of possible parameters connected to ripple currents that could influence battery ageing produce countless combinations that could be tested. For example, different DC/DC-converters with different current wave of forms such as bidirectional flyback converters or resonant converters could lead to new insights. Besides, changing the switching frequency could lead to different results as indicated in Section 2 in the same way different cell geometries, cell sizes and electrode materials or even electrolytes could lead to alternative behaviour if ripple current is induced. Nonetheless, the likelihood of current ripple not needing to be addressed carefully in practical applications could lead to lower development cost and less filtering effort in future energy storage systems. In [37,38] the component costs of power electronic systems are evaluated. Although the authors do not take batteries into account, their research is appropriate for a rough estimate. According to the studies, a cost reduction up to 20% or even 30% in some cases could be achieved because lighter and more compact filter capacitors and inductors could be used. By adding batteries, these values would be reduced fairly, ye<sup>t</sup> smaller filter capacitors and inductors still most likely lead to cheaper, lighter and more compact energy storage systems which could be a crucial, prospective benefit in highly competitive markets such as the automobile industry.

**Author Contributions:** Conceptualization, P.K.P.F.; data curation, P.K.P.F.; formal analysis, P.K.P.F.; investigation,P.K.P.F.; methodology, P.K.P.F.; resources, J.K.; software, P.K.P.F.; supervision, J.K.; validation, P.K.P.F.; visualization, P.K.P.F.; writing–original draft preparation, P.K.P.F.; writing–review and editing, J.K.;

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest. *Sustainability* **2019**, *11*, 6050
