Function: After the battery charging is completed, the liquid level will be reduced due to the consumption of electrolyte, which needs to be adjusted to the standard liquid level. The working principle of this device is that the suction acid tube is dropped into the battery, and then the battery is added with acid. The amount of acid is controlled by the time relay. After the acid is added, the excess acid is then sucked back into the acid box to make the level of liquid consistent and reach the standard level.