A radio-frequency (RF) coil assembly (120, 660) for acquiring magnetic resonance (MR) signals. The RF coil assembly may include one or more of: at least one radio-frequency (RF) receive coil (246-x) for acquiring the MR signals; a detune circuit (248-x) including one or more circuit arms (A, B) serially coupled to the at least one RF receive coil, each of one or more circuit arms having at least two low-loss switches (350, 352, 450, 452, 462, 466) serially coupled to each other; a charge control circuit (372, 472) coupled to each of the one or more circuit arms at a location that is between the at least two serially-coupled low-loss switches of each of the one of more circuit arms and configured to draw power from the RF receive coil during a detune state; and an energy storage device (252, 370, 470) coupled to the charge control circuit and configured to store the drawn power.