Hi i had purchased Development Tools Arria 10 SoC ( DK-SOC-10AS066S-A) for the real-time clock (RTC) its mentioned that we have to get Energizer 357-303HVZ Lithium coin battery with a nominal voltage of 1.55V , which is no longer available ,

Hello

Welcome to INTEL forum. It is advice to check for existing battery (Energizer 357-303HVZ Lithium coin battery ) datasheet to find for equivalent spec if the battery already obsolete. https://data.energizer.com/pdfs/357-303ZB.pdf

You should be able to find the existing battery full part number (to clarify the spec) from dev kit BOM list. Below is the BOM list path from dev kit installer

• \arria10_10as066n3f40_soc_v15.1.2\board_design_files\arria10_10as066n3f40_soc