I have started a couple of Google+ Hangouts on my cell phone (Android), and I can access them whenever I want.  I've been unable to find these Hangouts in a regular desktop web browser, though.  On the Google+ page  I can only start a new Hangout (icon on the left), but not access my existing chats.
Access old Google+ Hangout from web browser?
google plus;mobile;browser;google hangouts
This is not possible in the current version of Google+/the app.