Learn German: Das Handy muss man jeden Tag laden. - The mobile has to be charged every day.

In German, the subject doesn't have to be the first word. The subject here is man (one/you). Das Handy is the direct object receiving the action. Because Handy is a neuter noun, its accusative form looks identical to its nominative form. Putting the object in the first position just emphasizes the topic: 'As for the mobile phone, you have to charge it every day.'

The English translation uses a passive voice ("has to be charged"). Why does the German sentence use man?

Using the pronoun man with an active verb is a very common way in German to express a general rule or state that something must be done by someone. It often translates naturally to a passive voice in English. You could use a true passive here (Das Handy muss jeden Tag geladen werden), but using man is simpler and sounds very natural in everyday speech.

Why is the phrase jeden Tag in the accusative case?

When you specify a definite time using words like 'every', 'next', or 'last' without a preposition, German uses the accusative case. Because Tag is masculine (der Tag), 'every day' becomes jeden Tag.

I learned that laden means 'to load'. How do we know it means 'to charge' here?