I bought a spare battery.

我带备用电池了。

I hope you brought another torch or a spare battery.

我希望你多带了一只手电筒或备用电池。

Other intelligent mobile phone unless you got a spare battery or battery.

其他智能手机除非你准备了备用电池或外挂电池。

I hope you brought another torch or a spare battery. This one's at its last gasp.

我希望你多带了一只手电筒或备用电池。这个手电筒的电池快用完了。

The main control computer chip is connected with a spare battery to enable the system to work as before during power failure.

主控电脑芯片同时还接有一电池，作为备用电，使得本系统在停电时依旧工作。