The inventive subject matter provides a circuit and a method for efficiently charging a battery. In one aspect of the invention, the circuit includes an oscillator that generates a series of current pulses at a frequency that corresponds to a resonant frequency of the battery. Each pulse in the series includes ringing oscillations that includes a main pulse and a group of ringing decaying pulses. The group of ringing decaying pulses includes pulses with gradually smaller amplitudes over time until the pulses completely die out.