Abstract: In combination with an electric storage battery having a container and a cover, and having a plurality of walls for enclosing the electrolyte and other electrochemical components of the battery, a state of charge indicating device for monitoring the concentration of the electrolyte during the charge and discharge cycles of the battery. The indicating device is made of a porous solid support and an acid concentration sensitive dye which exhibits a change in color in accordance with the acid concentration of the electrolyte. The indicating device also includes a viewport located in one of the walls of the battery for viewing the color of the dye. The color may then be correlated to a reference scale to determine the state of charge of the battery.

Abstract: A sealed, rechargeable nickel-zinc cell includes a zinc electrode active mass essentially free of zinc metal when at full discharge, a carboxylated styrene-butadiene binder retaining the zinc electrode mixture in a coherent structure, a predetermined amount of cadmium being included in the zinc electrode mixture, a separator preferably comprising at least two layers of material free of any adhesive binding the layers together and a wicking layer positioned between the nickel positive electrode and the separator.