A charger comprising: a power source; a class E driver forming a resonant circuit having at least one resonant frequency, the class E driver comprising: a charging coil, wherein the charging coil is configured to magnetically couple with an implantable device to recharge the implantable device; a switch, wherein the switch is switched by the application of a first voltage to the switch, the switch comprising: a first node coupled to both the power source and the charging coil, and a second node coupled to a common reference point of the class E driver; a voltage sensor configured to sense a voltage across the switch between the first and second nodes; and a current sensor positioned to sense a current passing through the charging coil; and a processor electrically connected to the class E driver and configured to receive data from the voltage sensor indicative of the sensed voltage across the switch and data from the current sensor indicative of the current passing through the charging coil, wherein the processor is configured to control the switch via the application of the first voltage to the switch based on an identified current zero-crossing transition, and wherein the processor is configured to modify control of the switch based on the received voltage data indicative of the sensed voltage across the switch. a power source; a class E driver forming a resonant circuit having at least one resonant frequency, the class E driver comprising: a charging coil, wherein the charging coil is configured to magnetically couple with an implantable device to recharge the implantable device; a switch, wherein the switch is switched by the application of a first voltage to the switch, the switch comprising: a first node coupled to both the power source and the charging coil, and a second node coupled to a common reference point of the class E driver; a voltage sensor configured to sense a voltage across the switch between the first and second nodes; and a current sensor positioned to sense a current passing through the charging coil; and a processor electrically connected to the class E driver and configured to receive data from the voltage sensor indicative of the sensed voltage across the switch and data from the current sensor indicative of the current passing through the charging coil, wherein the processor is configured to control the switch via the application of the first voltage to the switch based on an identified current zero-crossing transition, and wherein the processor is configured to modify control of the switch based on the received voltage data indicative of the sensed voltage across the switch. a charging coil, wherein the charging coil is configured to magnetically couple with an implantable device to recharge the implantable device; a switch, wherein the switch is switched by the application of a first voltage to the switch, the switch comprising: a first node coupled to both the power source and the charging coil, and a second node coupled to a common reference point of the class E driver; a voltage sensor configured to sense a voltage across the switch between the first and second nodes; and a current sensor positioned to sense a current passing through the charging coil; and a processor electrically connected to the class E driver and configured to receive data from the voltage sensor indicative of the sensed voltage across the switch and data from the current sensor indicative of the current passing through the charging coil, wherein the processor is configured to control the switch via the application of the first voltage to the switch based on an identified current zero-crossing transition, and wherein the processor is configured to modify control of the switch based on the received voltage data indicative of the sensed voltage across the switch.