Nickel cadmium, secondary cell voltage

During charging, the secondary cell receives the same amount of electric energy as that previously released, and this is stored in the form of chemical energy (see Figure 1.11 for nickel-cadmium system). Terminal voltage, charging time, number... 

BATTERIES AND FUEL CELLS (SECTION 20.7) A battery is a self-contained electrochemical power source that contains one or more voltaic cells. Batteries are based on a variety of different redox reactions. Batteries that cannot be recharged are called primary cells, while those that can be recharged are called secondary cells. The common alkaline dry cell battery is an example of a primary cell battery. Lead-acid, nickel-cadmium, nickel-metal hydride, and lithium-ion batteries are examples of secondary cells. Fuel cells are voltaic cells that utilize redox reactions in which reactants such as H2 have to be continuously supphed to the cell to generate voltage. 

In battery systems based on aqueous electrolyte, water decomposition, which occurs above a cell voltage of 1.23 V, is such an unavoidable secondary reaction. But under certain conditions the resulting water loss can be avoided, and the system is used as a sealed one, as achieved with sealed nickel/cadmium, nickel/hydrogen, and nickel/metal hydride batteries. In lead-acid batteries corrosion is an additional unwanted secondary reaction with the consequence that lead-acid batteries cannot be made virtually sealed, but must have a valve, and a certain water loss cannot be prevented. 

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