Disclosed is a material of a kick-down drum comprising fine ferrite and microdispersion spheroidized cementite for an automobile also disclosed is a method for manufacturing the kick-down drum material. The supplemental heating system is configured for use in a recreational vehicle having a primary heating system that also heats the first fluid. First and second conductor are coupled to the power amplifier and to the power source, and have respective overlapping and non-overlapping portions on the circuit substrate. Measurement of the signal strength at each charging NFC antenna helps determine which charging coil should be utilized to effect the most efficient charging of the receiver.