XLS2CSV is a free xls to csv converter to bulk convert xls and xlsx files to csv files. It does not even needs Microsoft Excel or any Microsoft Excel alternatives on your computer for this xls to csv conversion.
XLS2CSV is extremely easy to use to mass convert xlsx or xls to csv. You start with specifying the folder which contains your excel files. You can choose to save converted files to a new directory, or overwrite existing ones. It can also maintain directory structure of original files.
Once you are done with this, click on “Start Conversion”, and it will bulk convert all the excel files in that folder to csv file. You can even choose to define your own separator characters for csv. If a workbook has multiple sheets, it will convert first sheet of that workbook.
XLS2CSV is a good free tool, and easy to use. If you want to later edit the converted CSV files, you can use free CSV Editor.