I know it will RTH when it loses contact with the remote after the time out expires- you set that in the settings, idk default settings but i had mine set at 10 seconds. After all, changes of it reconnecting are slim. I don't know about low battery conditions, I don't think it has that feature.
***Correction- yes it does have the RTH on low battery feature. After thinking about it for a minute I remembered it saving my rear a few times on some high altitude flight plans that required more battery than i had, so yes. Check your flight logs, look at the graph, note battery level, altitude, etc.