電池正在充電 = the battery is charging
例句：The charging LED light isn't on - I don't think the battery is charging.
Is it alright to leave the battery charging overnight?
Is it alright to leave/put the battery on charge overnight?
charging 是美語說法，on charge 是英式說法，建議使用前者。
電池沒電了 = the battery is dead/flat = the battery has no power
dead 是美語說法，flat 是英式說法。
例句：I left my car lights on all night and now the battery is dead. I need to jump my car.
電池變弱直到沒電 = 電池失去電力直到沒電 = to run the battery down = battery runs down
例句：You'll run the battery down if you leave your car lights on.
例句：My iPhone's battery runs down quickly after being fully charged. What should I do?
電池電力變弱 = the battery loses power