Abstract: A method for charging and simultaneously testing the condition of a nickel-cadmium accumulator wherein the charging cycle includes intervening measuring phases with discharging phases of relatively short duration. During the measuring phases, the internal resistance of the accumulator is measured under different charging and discharging conditions. The measured internal resistances are interrelated and additionally compared to internal resistances determined during successive measuring phases. The thus found relationships are used to derive therefrom a comprehensive spectrum of informations relating to various states of the accumulator, these informations being used for controlling the charging operation and permitting the state of usefulness of the accumulator to be assessed.