In this study, a test device is developed to measure the capacities and performances of high capacity battery banks and to detect broken cells. Batteries lose their performance over time due to their chemical properties, storage and usage conditions, production technologies. Some batteries may even become completely unusable long before the promised life cycle. Through this test device, the instant capacity of the battery banks is measured. Based on the data obtained, quantitative data such as state of health and nominal energy of the battery bank are calculating. It is determined whether the battery bank will meet the need according to its intended use. In this way, it is ensured to prevent possible losses by determining the battery cells or groups that need to be changed.