  We present an analysis of the availability and maximum extractable work of
quantum batteries in the presence of charge and/or heat steady-state currents.
Quantum batteries are modelled as non-interacting open quantum systems
(mesoscopic systems) strongly coupled to two thermal and particle reservoirs
within the framework of non-equilibrium Green's function theory in a
steady-state regime. We found that the battery can be charged manifestly by a
steady-state charge current compared to heat one, especially, in an
off-resonant transport regime. It allows us to reliably access the performance
of the quantum batteries in the high bias-charging regime.
