kaityuudentou no kandenti wo kaeru mae ni, konsento no basyo mo kakuninsita.

Because Verb (dictionary form) + 前に is the standard pattern for before doing something.

So:

• 乾電池を替える前に = before replacing the batteries

You do not normally use the past form here.
Compare:

• 出かける前に = before going out
• 寝る前に = before sleeping
• 食べる前に = before eating

So 替える前に is grammatically expected.

前に means before.

In this sentence, it connects the action 替える with the main action 確認した:

• 乾電池を替える前に、コンセントの場所も確認した。
• Before replacing the batteries, I also checked where the outlet was.

It marks the earlier point in time relative to the main action.

Here, の links two nouns and shows a relationship between them.

• 懐中電灯 = flashlight
• 乾電池 = battery / dry cell
• 懐中電灯の乾電池 = the flashlight’s batteries / the batteries for the flashlight

This の is not limited to possession. It can also mean things like:

• belonging to
• part of
• used for
• associated with

So here it means the batteries associated with the flashlight.

Because 乾電池 is the direct object of 替える.

• 乾電池を替える = replace the batteries

The whole noun phrase is:

• 懐中電灯の乾電池 = the flashlight’s batteries

and then を marks that entire phrase as the thing being replaced.

So the structure is:

• [懐中電灯の乾電池] を 替える

not

• replace the flashlight

but

• replace the flashlight’s batteries

This is a very common learner question.

Both can be read かえる, but they mean different kinds of change.

• 替える = replace one thing with another
• 変える = change/alter something

For batteries, 替える is the natural choice because you are swapping old batteries for new ones.

Examples:

• 電池を替える = replace the batteries
• 服を着替える = change clothes

By contrast:

• 予定を変える = change the schedule
• 考えを変える = change one’s mind

So in this sentence, 替える is the correct kanji and meaning.

も means also or too.

So:

• コンセントの場所も確認した
• I also checked the location of the outlet.

The implication is that checking the outlet location was an additional action. Something else was done or checked as well, and this was one more thing.

Without も, the sentence would simply say:

• コンセントの場所を確認した
• checked the location of the outlet

With も, it becomes:

• also checked the location of the outlet

Because 確認した is the main verb of the whole sentence, so it carries the tense.

• 確認した = checked / confirmed

The phrase 乾電池を替える前に is a subordinate time expression, and in Japanese, the verb before 前に stays in the plain non-past form.

So the tense logic is:

• before replacing the batteries → subordinate phrase
• checked the outlet location → main action, marked as past

This is very normal in Japanese.

It can mean either, depending on context.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do.

So 乾電池 can mean:

• battery
• batteries

In this sentence, a flashlight often takes more than one battery, so English may naturally translate it as batteries, but the Japanese itself does not explicitly mark plural.

No. Even though it comes from English originally, Japanese コンセント does not mean consent.

In Japanese, コンセント means:

• electrical outlet
• power socket

This is a classic example of a borrowed word whose meaning changed in Japanese.

So:

• コンセントの場所 = the location of the outlet/socket

A learner should be careful not to interpret it as the English word consent.

Because the speaker is specifically checking where the outlet is, not just checking the outlet itself.

• コンセントを確認した could mean checked the outlet
• コンセントの場所を確認した means checked the location of the outlet

Adding 場所 makes the sentence more precise.

確認する means to check, confirm, or make sure of something. It sounds more deliberate than simply 見る.

Compare:

• 見た = looked / saw
• 確認した = checked / confirmed / made sure

So コンセントの場所も確認した suggests the speaker intentionally made sure where the outlet was, perhaps for practical reasons.

No, the subject is not explicitly stated.

Japanese often omits subjects when they are understood from context. So the sentence does not literally say I, he, or she.

The subject is inferred from the situation. In many textbook translations, it may become:

• I also checked the location of the outlet before replacing the flashlight batteries.

But that I is supplied by context, not directly written in the Japanese sentence.

Yes, it is completely normal Japanese word order.

The sentence is structured like this:

• [懐中電灯の乾電池を替える前に]、[コンセントの場所も確認した]

That is:

• Before replacing the flashlight batteries,
• also checked the location of the outlet.

Japanese often places time and condition phrases before the main verb, and the main verb usually comes near the end of the sentence. So although it may feel unusual from an English point of view, this is standard Japanese structure.