Introduction. At this stage of the continuous development of combined power supply systems there is a problem of improving the methods and electrical devices aimed at the accumulation of energy and its dynamic transmission to consumers. In modern modes of operation of electric vehicles (EV), energy storage devices must withstand millions of cycles of charge / discharge without degradation of electrical characteristics. Supercapacitors (SP) can process at least one million cycles and can be used in combined power supply systems of the EV and various electrical and electromechanical objects that are stochastically in need of high pulse power. Problem statement . In combined power supplies from the SC and accumulator battery (AB) combine high performance with the specific power of the SC with high energy specific AB, which can easily provide high power at the beginning of the movement of the EV or at a sharp change in the speed of movement, while providing the required energy storage with AB in long motion. Using combined systems with SC and AB can significantly increase the life of AB and work with low losses in circuits oscillatory charge SC. The purpose of this work is to develop the theory of energy processes in the circle of the oscillatory charge SC from AB, which is based on the consideration of the dependence of the capacity of the SC on the voltage on their terminals and the purposeful change of the initial voltages of their charge, which improves the energy efficiency of the combined power supply systems. Results. In this work, a study of the energy characteristics in the circuits of the oscillatory charge of supercapacitors from a storage battery, which is considered as a real source of electromotive force (EMF), has been carried out. A comparison of the power characteristics of circuits of oscillatory charge SC with different values ​​of the quality factor of the charging circuit is carried out. The approximated solution of the nonlinear nonuniform differential equation of the second order for an oscillatory process of charge SC from AB, in which the capacitance is a linear function of the voltage at its terminals is obtained, which makes it possible to determine the dependence of energy losses in charge circles on the parameters of their elements. Conclusions. The conditions for increasing the energy transfer coefficient from AB to SC in the circuits of the oscillatory charge are analyzed. The features of the influence of the initial voltages, capacities and Q-factor of the charging circuit on the energy transfer coefficient from AB to SC are determined. The regularities of increasing the energy transfer coefficient and reducing the power losses in the circuits of the oscillatory charge from the SC from AB with the increase of the effective Q-factor of the charge circuit and the initial voltages on the terminals of such a SC are established.