In one embodiment, a depassivating circuit includes a battery, a resistive load coupled to the battery, and a magnetic field sensor. The magnetic field sensor detects a presence of a magnetic field. The magnetic field sensor depassivates the battery by causing current from the battery to flow through the resistive load, in response to the presence of the magnetic field. The magnetic field sensor detects removal of the magnetic field. The magnetic field sensor ends depassivation of the battery, in response to the removal of the magnetic field.