Publisher Summary This chapter provides an overview of nickel batteries. It discusses various types of nickel batteries, such as: nickel-cadmium secondary batteries, nickel-iron secondary batteries,, and sodium-nickel chloride secondary batteries. The nickel-cadmium battery is mechanically rugged and long lived. In addition, it has excellent low-temperature characteristics and can be hermetically sealed. Cells using the nickel-cadmium couple can be divided into two main groups: cells having thick plates and cells with thin sintered plates. Whereas, nickel-iron batteries offers very long cycle life but, primarily as the result of the iron electrode, a low energy density at high discharge rates has made this system unattractive for electric vehicles. The sodium-nickel chloride secondary batteries are newly developed cells. Their open circuit voltage is about 2.6 V in the 200-300°C temperature range. The theoretical energy density is about 750 W h/kg-1 against practically realized values of 100Wh/kg-1.