"My battery is flat." is common way to say your phone ran out of battery in UK English. The word "flat" in this case implies the batter is no longer working.
"My phone ran out of charge." is also common way to phrase this in UK English. "Charge" refers to the battery power in this case.
"My battery is flat."
（充電が切れてしまった）
これは、[ケータイの充電が切れてしまった](https://eikaiwa.dmm.com/uknow/questions/8103/)時に、
イギリスでとてもよく使われる表現です。
この "flat"とは、この場合[電池](https://eikaiwa.dmm.com/uknow/questions/51278/)がもう長くありません、
という意味になります。
"My phone ran out of charge."
（ケータイの[充電](https://eikaiwa.dmm.com/uknow/questions/47658/)が切れてしまった）
これもまた、イギリスではよく使われる表現です。
この場合 "Charge"は電池/バッテリーの事を意味しています。
I'm sorry about not replying to your message, my phone died.
When a friend sends you a message but your battery runs out before you can reply and you want to apologize to them you can say... "I'm sorry about not replying to your message, my phone died."
友達からメールが来て、返事をする前に充電が切れてしまって返事ができなかった事を謝りたい場合、つぎの様に言うことが出来ます。
【例】
"I'm sorry about not replying to your message, my phone died."
（返事ができなくてごめんなさい、ケータイの充電が切れてしまって）
Sorry I didn't reply. My battery was dead.
Sorry I didn't reply. My battery was flat.
Sorry I didn't reply. My phone ran out of charge.
You could also say sorry I didn't reply my phone died.
Sorry I didn't reply. My battery was dead.
（返事しなくてごめんなさい。充電がなくなったんです）
Sorry I didn't reply. My battery was flat.
（返事しなくてごめんなさい。充電がなくなったんです）
Sorry I didn't reply. My phone ran out of charge.
（返事しなくてごめんなさい。充電が切れたんです）
ほかに「Sorry I didn't reply, my phone died（返事しなくてごめんなさい。充電が切れたんです。）」と言うこともできます。
Friend, I'm sorry. My phone died before I could reply
When you want to apologize to your friend for not responding immediately because your phone died, then you can say:
-I'm sorry, my battery died before I could respond
-Friend, I'm sorry. My phone died before I could reply
-My apologies for the late response, my battery died.
充電が切れたのですぐに返信できなかった、という事を伝える場合には以下のように言うことができます。
-I'm sorry, my battery died before I could respond
（ごめん、返信する前に充電がきれてしまったよ。）
-Friend, I'm sorry. My phone died before I could reply
（ごめんね。返信する前に充電が切れてしまったよ。）
-My apologies for the late response, my battery died.
（返信が遅くなってごめん、充電が切れちゃって。）
My battery died, so I was unable to reply back to you.
I am sorry but my phone died and I had no way of reaching you.
The battery went out on my phone, and I was unable to charge it.
"My battery died, so I was unable to reply back to you." This expression lets you know that they could not get back to you because their phone was dead at the time. "I am sorry but my phone died and I had no way of reaching you." This expression explains the same thing only in a different context. "The battery went out on my phone, and I was unable to charge it." also this expression lets said person know that they had no way of reaching them since their phone was dead.
"My battery died, so I was unable to reply back to you."
ー充電が切れたので、返事が遅くなった。
この表現は、充電切れのため連絡ができなかった、ということを表現しています。
"I am sorry but my phone died and I had no way of reaching you."
ーごめんなさい、電話の充電が切れていたので連絡の術がありませんでした。
この文章も上記と同じ意味ですが、言い回しが少し違います。
"The battery went out on my phone, and I was unable to charge it."
ー電話の電池が切れたけど、充電のしようがなかった。
この文章も電話の充電がなくなったので連絡ができなかった、ということを相手に伝える事ができます。
Sorry for not responding in time, my cell phone battery died.
I apologize for not responding immediately to your text message, my cell phone battery died.
Rechargeable batteries, including those of cell phones, have the nasty habit of becoming flat at the most crucial times, for example, when you are required to immediately respond to a text message that your boss has just sent you. This can stress you a lot and send you into a state of panic looking for your cell phone charger everywhere. It can even be more frustrating if you are driving and do not have a cell phone charger in your car. So, when you finally get your cell phone battery charged, you may respond to the text message and say:
Sorry for not responding in time, my cell phone battery died.
or
I apologize for not responding immediately to your text message, my cell phone battery died.
携帯電話などに使われる充電式の電池は、例えば「上司のメールに即座に返信しなければいけないとき」など、大事な時に限って切れたりしますね。
このような場合は、多大なストレスを感じ、パニックになりながら充電器を探すことでしょう。
これが、車の運転中で充電器が車に置いていない場合だと余計にイライラするでしょう。
ようやく携帯の充電ができ、相手に返信をする際には以下のように書くと良いでしょう。
Sorry for not responding in time, my cell phone battery died.
ー携帯の充電が切れていて、すぐに返信ができずにすみません。
I apologize for not responding immediately to your text message, my cell phone battery died.
ー携帯の充電が切れていてすぐに返信ができずに申し訳ありませんでした。
こんにちは。
様々な言い方ができると思いますが、例えば次のような英語表現はいかがでしょうか：
Sorry, my phone ran out of battery.
Sorry, my phone died.
my phone died は直訳すると「電話が死んだ」となりますが、「充電が切れた」という意味の少しカジュアルな英語表現です。
ぜひ参考にしてください。
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