Wǒde shǒujī méi diàn le.
我的手机没电了。
The battery of my mobile phone is dead.
Notes:
我的(wǒde): my
手机(shǒujī): mobile phone
没(méi): have no
电(diàn): electricity, battery
了(le): particle word
Example:
A:我的手机没电了。你有充电器吗?
Wǒde shǒujī méi diàn le. Nǐ yǒu chōnɡdiànqì mɑ?
The battery of my mobile phone is dead. Do you have a changer?
B:不好意思,没有。
Sorry, I haven't.