Abstract: This paper proposes a design of the thermal control system with 5 five silver zinc batteries of various cell number and electric currents to be used in an upper stage vehicle. Firstly, the adiabatic calorimetry is used to determine the heat capacity and the thermal consumption of a representative battery, along with the relationship between its thermal consumption and the electric current. Then, effective measures are taken to reduce the heat leak, and the background heat leak of the system is measured for accurately determining the heat loss. In the end, by balancing the applied area of two kinds of thermal control coatings to ensure a proper equivalent emittance of the battery’s surface, the battery is designed to maintain in a room temperature range. The telemetry data show that the above goal has been achieved.