Quantum versus classical many-body batteries

Quantum batteries are quantum-mechanical systems with many degrees of freedom which can be used to store energy and that display fast charging. The physics behind fast charging is still unclear. Is it just due to the collective behavior of the underlying interacting many-body system, or does it have its roots in the quantum-mechanical nature of the system itself? In this work we address these questions by studying three examples of quantum-mechanical many-body batteries with rigorous classical analogs. We find that the answer is model dependent and, even within the same model, depends on the value of the coupling constant that controls the interaction between the charger and the battery itself.