Tror du att batteriet räcker tills vi kommer hem?

Because this is a yes/no question in Swedish. In main clauses, Swedish usually puts the finite verb first in yes/no questions.

• Statement: Du tror att batteriet räcker.
• Question: Tror du att batteriet räcker?

So tror comes before du because the speaker is asking Do you think ...?

Att here means that and introduces a subordinate clause:

• Tror du att batteriet räcker ...
• Do you think that the battery will last ...

In everyday Swedish, att is often included here and sounds very natural. Sometimes it can be omitted in speech, especially in casual language:

• Tror du batteriet räcker tills vi kommer hem?

That is also understandable and common, but att is the safe and standard choice for learners.

Because batteriet is the definite form of ett batteri.

• ett batteri = a battery
• batteriet = the battery

Swedish usually adds definiteness as an ending, rather than using a separate word like the.

Since the speaker means a specific battery already known in the situation, Swedish uses batteriet.

Räcker is the present tense of räcka.

In this sentence, räcka means something like:

• to be enough
• to last
• to be sufficient

So batteriet räcker means the battery is enough / will last.

This verb is very common in Swedish for talking about time, money, food, power, and so on:

• Pengarna räcker inte. = The money isn’t enough.
• Maten räcker till alla. = The food is enough for everyone.

Here, with a battery, the natural English equivalent is usually will last.

Swedish often uses the present tense to talk about the future, especially when the future is clear from context.

So:

• Tror du att batteriet räcker ...
  can mean
• Do you think the battery will last ...

This is very normal Swedish. You do not need a separate future form like English will in many cases.

Tills means until.

It connects the idea of the battery lasting with the point in time when we get home:

• batteriet räcker tills vi kommer hem
• the battery lasts until we get home

A close synonym is tills dess att, but tills is much more common in everyday speech.

Again, Swedish often uses the present tense where English uses a future form.

So:

• vi kommer hem literally looks like we come home
• but it means we get home / we come home

After time words like när, innan, tills, and similar conjunctions, Swedish very often uses the present tense for future meaning.

Because hem often works as an adverb meaning home in the sense of going home.

• komma hem = come/get home
• gå hem = go home
• åka hem = go home / travel home

You do not normally say till hem.

Also, hem and hemma are different:

• hem = movement toward home
• hemma = being at home

So:

• Vi kommer hem. = We get home.
• Vi är hemma. = We are at home.

Yes. Both att batteriet räcker and tills vi kommer hem are subordinate clauses.

The basic order here is still:

• subject + verb
• batteriet räcker
• vi kommer

A very important Swedish rule is that sentence adverbs like inte usually come before the verb in subordinate clauses.

For example:

• Tror du att batteriet inte räcker tills vi kommer hem?
  = Do you think the battery won’t last until we get home?

Notice:

• main clause: Batteriet räcker inte.
• subordinate clause: att batteriet inte räcker

That difference is something learners often need to watch carefully.

Yes, you often can, especially in spoken Swedish.

Both are possible:

• Tror du att batteriet räcker tills vi kommer hem?
• Tror du batteriet räcker tills vi kommer hem?

Including att sounds a bit fuller and is very standard. Omitting it can sound a bit more conversational.

For a learner, using att is usually the easiest and safest habit.

The most natural negative version is:

• Tror du att batteriet inte räcker tills vi kommer hem?

This means:

• Do you think the battery won’t last until we get home?

Notice the placement of inte:

• in the subordinate clause, it comes before räcker

That is a classic Swedish subordinate-clause pattern.

It is fairly straightforward. The common forms are:

• infinitive: räcka
• present: räcker
• past: räckte
• supine: räckt

Examples:

• Batteriet räcker. = The battery lasts / is enough.
• Batteriet räckte hela dagen. = The battery lasted all day.
• Har det räckt? = Has it been enough?

Not always. In careful speech, att may be pronounced clearly, but in everyday spoken Swedish it is often reduced and can sound very weak.

So learners may hear something closer to:

• Tror du batteriet räcker ... or
• Tror du a batteriet räcker ...

This is normal. Even if the full spelling is att, the pronunciation is often lighter than English speakers expect.

A good summary would be:

1. Verb-first question word order

   • Tror du ...?

2. A subordinate clause introduced by att

   • att batteriet räcker

3. Definite noun with an ending

   • batteriet = the battery

4. Present tense used for future meaning

   • räcker
   • kommer

5. Time clause with tills

   • tills vi kommer hem

6. Motion word hem instead of hemma

   • komma hem = get home

If you understand those six points, you understand most of what makes this sentence work.