Learn Farsi: همکار من اعلام کرد که باتری بی‌سیم تمام شده است. - My colleague announced that the radio's battery had run out.

In Farsi reported speech, you keep the exact tense the original speaker used. The colleague likely said, 'The battery has run out' (باتری تمام شده است). So, even though the reporting verb اعلام کرد (announced) is in the past tense, the reported clause stays in the present perfect. Farsi doesn't shift the tense backward like English does.

What does بی‌سیم mean, and why is it translated as radio?

بی‌سیم literally translates to 'without wire' (بی = without, سیم = wire). While it can mean 'wireless' as an adjective, as a noun it is the standard word for a two-way radio or walkie-talkie.

Could I use مردن (to die) for a battery running out, like we do in English?

No, Farsi doesn't typically say a battery 'died.' Instead, you use the compound verb تمام شدن (to finish / to run out). Here, تمام شده است literally means 'it has finished' or 'it has become finished.'

How are the words for battery and radio connected in this sentence?

They are connected by the hidden ezafe vowel, which links nouns to show possession. You pronounce it as باتریِ بی‌سیم (bātri-ye bisim), meaning 'the battery of the radio.' Because باتری ends in a vowel sound, the ezafe is pronounced as '-ye'.