The watch's battery is worn down.
1 battery 电池
replace the battery
The battery is flat.
a battery of..
He faced a battery of questions.
2 worn down 磨损不堪的；疲惫不堪的..
My heels of my shoes have worn down.
After the race,he is worn out.
A:What can I do for you?
B:Yes.There is something wrong with my watch.It stopped several hours ago.
A:Let me have a look.The watch's battery is worn down.
B:How much is a battery?
B:How long will it last?
A:About 2 years.