The internal resistance of all sealed battery is the smaller, the smaller the internal resistance, the stronger the large current discharge capacity, and the more fully the electric energy is released.

　　Any power supply more or less has a certain internal resistance. In order to improve the load-carrying capacity, we hope that the internal resistance of the power supply is as small as possible.

　　The resistance r is the internal resistance of the car battery, and RL is the load, which is in series with the internal resistance r of the battery, and the current flowing through r is equal to the load current. Assuming that the magnitude of r is constant, the greater the load current, the greater the current flowing through the internal resistance r, and the higher the voltage across r so that the voltage across the load RL decreases. If the voltage drop is too large, it may even cause the RL to fail to obtain the rated working voltage and fail to work normally. Therefore, we hope that the internal resistance of the battery is as small as possible so that when a heavy load is driven, there will be no significant voltage drop on the internal resistance.

　　The internal resistance of the battery will increase with the use of time, especially for the battery that is about to be scrapped, the internal resistance will increase significantly. At this time, although the battery voltage is higher after fully charged, the internal resistance becomes larger. When a large current load is applied, a large voltage drop will be generated on the internal resistance, thereby reducing the voltage across the load.