  The collective and quantum behavior of many-body systems may be harnessed to
achieve fast charging of energy storage devices, which have been recently
dubbed quantum batteries. In this paper, we present an extensive numerical
analysis of energy flow in a quantum battery described by a disordered quantum
Ising chain Hamiltonian, whose equilibrium phase diagram presents many-body
localized (MBL), Anderson localized (AL), and ergodic phases. We demonstrate
that i) the low amount of entanglement of the MBL phase guarantees much better
work extraction capabilities than the ergodic phase and ii) interactions
suppress temporal energy fluctuations in comparison with those of the
non-interacting AL phase. Finally, we show that the statistical distribution of
values of the optimal charging time is a clear-cut diagnostic tool of the MBL
phase.
