Although I have no active accordions at the moment, I do have bootstrap tabs and all of the hidden content within the tabs is crawled.  To test your own page, go to webmaster tools and Fetch as Google. When fetching is done, click on the page link and select the tab "Fetching". This shows all of the HTML crawled and you can verify that the content in the accordion has been crawled. You also mentioned "penalty". Google's policy on penalties for hidden content is here: https://support.google.com/webmasters/answer/66353?hl=en.  Google would not consider tabs and accordions containing legitimate content (no white text etc.) to fall under this "Hidden text and links" category.