In the article we propose the new method of increasing the accuracy of the estimation of internal resistance and estimation of the residual capacitance of battery, taking into account the duality of the regime of battery. The estimation of the internal resistance of battery is widespread, but without research of the influence of the regime of battery. The duality of battery assumes a change in the activity of electrochemical active masses, which is examined in this work. In the article examined method of evaluating of residual capacitance of battery according to the value of internal resistance realized without presence of known model of battery. The method of determining of residual capacitance and internal resistance into one express test for the unknown battery without the extraction of the system is considered. Analysis of dependence, obtained in a research, leads the estimation of the internal resistance of battery to the point of testing. This makes it possible to reveal the connection of the point of testing with the residual capacitance.