Once water enters into a battery, it is very difficult to get it out due to the battery’s safety vent (which doesn’t allow any liquids to leak out of the battery). Therefore, if water enters the cell and is kept around the terminal, it could induce the battery to malfunction.
In the worst case, it will result in leakage due to damage to the sealing. It is recommended to immediately dispose of batteries that have made contact with water to prevent the failure of the cells and the subsequent appliances they are used in.
It is very unlikely that batteries will start to leak in a washing machine. If this does occur and liquid leaks out of a battery due to it ending up in a washing machine, it will not cause any serious issue because the liquid becomes greatly diluted in all of the water from the washing machine. However, it is highly recommended to wash the clothing again in fresh water.