Entity Translation and Field Collection Entity Translation exposes a checkbox on fields, entitled:


  Users may translate all occurrences of this field


When dealing with a Field Collection field, which of the following should I check the box for?


Only the field collection field
Only the child fields
Both the field collection field, and its child fields
Field Collection doesn't support Entity Translation, so my advice is to find another way to achieve your aim. 

There is a patch available which has been under development for a long time, use at your own risk. 

The Drupal.org issue with it's accompanying patch can be found here:
https://www.drupal.org/node/1344672