Batteries are a device that can convert the chemical energy it stores into electrical energy that can be used by an electronic device. One of the battery types is NiMH battery. This paper explains what NiMH batteries are, their characteristics, and their uses. One example of the use of NiMH is the NiMH battery as a storage place for electrical energy for a hybrid car. However, this battery ideally operates at 25°C. Room temperature that is too high can shorten battery life. This occurs in the tropics which have high humidity characteristics above 30°C and temperatures that are above room temperature. This causes the electric car battery to only last for five years, in contrast to the subtropical regions that can last for 10 years. Allegedly the cause is the ineffectiveness of the cooling system in providing a suitable temperature for the battery. In this paper, the room temperatures measured are above 30°C and the battery voltage experiences the reduction. It is proven that the temperature affects the voltage of the battery.