Publisher Summary This chapter discusses two types of zinc -halogen batteries: zinc-chlorine secondary batteries and zinc-bromine secondary batteries. The rechargeable zinc-chlorine battery currently under development by Energy Development Associates, Michigan is proposed as a new approach to energy saving power systems for vehicles. This is an interesting new concept in battery design, which proves to have applications in the small-battery field. The object that Energy Development Associates have in mind is to produce a battery capable of propelling a 1 tonne vehicle 322 km at a steady speed of 80.5 km/h with 120km/h excursions. Experimentally, it is found that, with a 50 kWh, 363 kg battery system, the vehicle could accelerate from 0 to 64 km/h in 10 s. This requires a minimum power density of 10W/kg. To maintain an average speed of 80.5 km/h on level ground requires 12 kW, equivalent to an energy density of 23 W h/kg. At a 4 h discharge rate, this yields a 322km range between charges. On the other hand zinc-bromine secondary batteries are also in development mode and has potential in future application in load travelling and vehicle propulsion. The theoretical density is 430Wh/kg-1 against a practically realized value of 15-85W/kg-1.