Technically "a battery" would be "một cục pin" whereas "pin" in general should be "batteries".
The word is used to classify typically rock or pebble like objects but it can extend to other shapes such as a battery and even uh... poop.
What about "I need THE battery"? Is it incorrect because there's no classifier?
I agree . The battery .
Why does "I need the battery for my clock" not work
--the-- battery -- a-- battery -where is the classifier-?