The fundamental reactions in accordance with the generally accepted ``double-sulphate'' theory of storage battery charging are comparatively simple. Additional reactions and phenomena, such as gas evolution, acid concentration, heating, and local action are factors which affect charging conditions. Data showing the effects of these factors are given in this paper. The ampere-hour law regarding charging rates is illustrated. Results of constant voltage and modified constant voltage charging are given, and constant voltage floating and trickle charging are discussed. Various means of automatic control for charging batteries in different classes of service are given, some of these schemes involving the use of ampere-hour meters and voltage relays.