The car won't start because its battery, or it's battery, is dead?
How to Remember It:
The word it's means "it is" or "it has," while its means "belonging to it."
In the sentence above, "it is battery" or "it has battery" doesn't work – so the correct version has to be its.
Similarly, in the sign shown here, "it is/has accessories" and "it is/has enclosure" don't make sense, so it's wasn't the right choice.