Batteribyttet skjer før rensingen.

Because Norwegian normally writes compound nouns as a single word.

So:

• batteri = battery
• bytte = change / replacement

Together they make batteribytte = battery replacement.

Then the definite ending is added to the whole compound:

• et batteribytte = a battery replacement
• batteribyttet = the battery replacement

This is very typical in Norwegian. English often uses separate words where Norwegian prefers one compound word.

It marks the noun as definite singular.

The base noun is:

• et batteribytte = a battery replacement

Definite form:

• batteribyttet = the battery replacement

The reason it takes -et is that the head noun bytte is a neuter noun in Norwegian. In compounds, the final part usually determines the gender, so batteribytte is also neuter.

Because the sentence is talking about specific steps or processes, not just any battery replacement or any cleaning.

• batteribyttet = the battery replacement
• rensingen = the cleaning

In instructions, technical writing, or descriptions of a procedure, Norwegian often uses the definite form this way when the steps are understood from context.

A more general version would be something like:

• Et batteribytte skjer før en rensing

But that sounds much less natural for a specific procedure. The original sentence sounds more like the battery replacement happens before the cleaning step.

Skjer is the present tense of å skje, which means to happen, to occur, or to take place.

So:

• Batteribyttet skjer før rensingen.
• Literally: The battery replacement happens before the cleaning.

This verb is often used for events, processes, or steps in a sequence. It sounds natural in formal or procedural language.

Because Norwegian is expressing this as an event that takes place, not simply describing a state.

• skjer = happens / takes place / occurs

Using er would not mean the same thing.
For example, Batteribyttet er før rensingen would sound wrong.

So skjer is the right choice when talking about the order of actions or procedures.

No. It is not a passive sentence.

The subject is batteribyttet (the battery replacement), and the verb is skjer (happens). So the sentence is talking about an event.

It does not mean the battery is replaced before the cleaning in a grammatical passive sense.

A passive version would be something like:

• Batteriet blir byttet før rensingen. = The battery is replaced before the cleaning.
• Batteriet byttes før rensingen. = The battery is replaced before the cleaning.

So the original sentence focuses on the replacement as a step, not on the battery as an object.

Here før means before and is followed by a noun phrase:

• før rensingen = before the cleaning

So in this sentence, før is functioning like a preposition.

It can also introduce a clause:

• før vi renser den = before we clean it
• før den blir renset = before it is cleaned

So:

• før + noun → før rensingen
• før + clause → før vi renser den

Yes, and that would be natural, but it is not exactly the same in focus.

• Batteribyttet skjer før rensingen
  Focus: the battery replacement as a step or event

• Batteriet byttes før rensingen
  Focus: the battery being replaced

In many real contexts, the practical meaning is very similar. But grammatically, the original sentence is more about the procedure, while the alternative is more about what is done to the battery.

Yes:

• Før rensingen skjer batteribyttet.

That is grammatical. When a time expression is placed first in a Norwegian main clause, the finite verb still has to stay in second position. This is the normal V2 word order pattern in Norwegian.

So:

• Batteribyttet skjer før rensingen.
• Før rensingen skjer batteribyttet.

Both are correct. The original version is more neutral. The fronted version gives extra emphasis to before the cleaning.

Because in Bokmål, many nouns ending in -ing can be treated as feminine, and then the definite singular can end in -a.

So you may see:

• rensingen
• rensinga

Both can be correct in Bokmål, depending on style and preference.

Very roughly:

• rensingen can sound a bit more neutral or formal in many contexts
• rensinga can sound more colloquial or more clearly feminine

So if you encounter Batteribyttet skjer før rensinga, it means the same thing.