"Zij hadden de goede batterijen niet gevonden."
Translation:They had not found the good batteries.
Couldn't this be understood as "They had not found the right batteries", i.e. the batteries that are compatible with a particular device? That's how I read it at first. Earlier in the course we had "Dit is niet het goede document" which was translated as "This is not the right document".
Except for a few exceptions:
- article included in English = article included in Dutch
- article not included in English = article not included in Dutch
Exceptions are occupations, which need the article in English, in Dutch it's optional. Then there are some fixed situations, for instance "de aarde" needs the article in most cases, while it can be left out in English: "Earth".