Yesterday, a friend came and told me how to test battery performance.
He drove the car mostly on petrol, without consuming the battery so the battery gets full. (Bars become full and green). if battery is powerful then it must get full in 2 to 3 kms.
After that he put car in ECO mode, and drove the car on battery. Then drove around 2.7 KMs just on battery.
He said if battery is powerful, then car must go at least 2 KMs on battery alone.
Car is 2nd Gen Prius.