Learn Turkish: Batarya henüz tamamen boş değil. - The battery is not completely empty yet.

In Turkish, pil is generally used for standard removable or disposable batteries (like AA batteries for a remote). Batarya refers to a rechargeable battery pack or a built-in system, like those in smartphones, laptops, or electric vehicles. This sentence is likely talking about an electronic device.

Does henüz always mean "yet", and does it have to be used with a negative word like değil?

Henüz is most often used in negative sentences to mean "yet" (as in "not yet"). However, you can also use it in positive sentences, where it means "just" or "recently" (for example, Henüz geldi means "He just arrived").

How is tamamen (completely) formed? Is it related to tam (full)?

Yes! Tam means "full", "complete", or "exact". The -en suffix at the end of tamamen turns it into the adverb "completely", answering the question of "how much" or "to what degree". This specific suffix comes from Arabic and is used to create a few other common Turkish adverbs, like gerçekten (really) or kısmen (partially).

Could I change the word order to "Batarya tamamen henüz boş değil"?

It would sound unnatural. In Turkish, adverbs of time (like henüz) generally come before adverbs of degree or manner (like tamamen). The current order smoothly builds the description: first the time frame, then the degree, then the state being described.