You are on the right track; the singular conocimiento is more general and abstract (knowledge, awareness), while the plural conocimientos refers more to knowledge about a particular topic (skill).
A very good idea when faced with words with subtle shades of difference in translation is to look for translations in context, in real texts rather than a dictionary; I use Linguee.com a lot for that. For conocimiento, you find as primary translations "knowledge", "understanding" and "acquaintance", and then in the translated real-world sentences, "awareness". Then of course there's also the related meaning "consciousness" (as in recuperar el conocimiento "to regain consciousness, to come to"), but that's another thing. There are some fixed phrases where you can only use the singular form, such as
- tomar conocimiento de "to become acquainted with, to become aware of, to inform oneself about"
- poner en conocimiento de "to make (someone) aware of", etc.
- ser de público conocimiento "to be public knowledge"
The plural conocimientos is translated more as "expertise" and "skills", "know-how", etc.
As you see conocimiento is sometimes associated with passive awareness rather than knowledge gained by active learning, but that's only common practice, not a requirement; it's OK to use conocimiento to refer to actively accumulated knowledge. There are many instances in which you can use the singular and the plural interchangeably, but the plural is more specific and tends to be specified as belonging to a certain area, as well. Compare:
- Tengo conocimientos de carpintería. "I have carpentry skills."
- Tengo un conocimiento básico de la carpintería. "I have a basic knowledge of carpentry."
- Tiene un profundo conocimiento de la historia del lugar. "He has a profound knowledge of the history of the place."
- Tiene muchos conocimientos sobre agricultura. "He knows a lot about agriculture."
You could say that conocimiento (singular) is closer to the meaning of "lore", while conocimientos (plural) is closer to the meaning of "skill".
There are issues of collocation, i.e. how you pair up the words. Back to my examples, you cannot say
- *Tengo conocimiento de carpintería.
- *Tiene profundos conocimientos de la historia del lugar.
You have conocimiento of general topics (i.e., you know about them) or of situations (i.e., you are aware of or informed about them). You have conocimientos of particular disciplines (i.e., you have skills). Again, sometimes these overlap. You'll surely get it as you're faced with more real-life examples.