Now, we all know when you really need batteries, they're dead.

现在，我们都知道，当你真需要电池时它们总没电。

youdao

You are obviously only human and will need to recharge your batteries every now and then, but that doesn't mean that not publishing blog posts for several days in a row is the way to go.

你当然也只是普通人，经常需要休息，但这并不意味着你可以连续好几天不更新博客。

youdao

When you're in the mountains and you need your flashlight because it's really an emergency, it just so happens that the batteries are dead.

当你在山里,因紧急情况需要手电筒时,情况偏偏就是,电池没电了。

youdao

I can take you and immediately start designing batteries, because we need ions in motion, we need small ions in motion.

我可以从此让你快速起步设计电池，因为我们需要能运动的离子，我们需要能运动的小型离子。

麻省理工公开课 - 固态化学导论课程节选

Simply add the number of batteries you need to your bank to cover the power requirement needed to cover the usual yard work time -and the rest of the time, the batteries would be in the rack trickle charging until needed.

FORBES: Outdoor Power Equipment Goes Gas-Free: Makes Way To Wind Energy

Not only do you need to worry about exploding batteries, a new article in London's Daily Mail claims that "girls as young as 12 are being diagnosed with nerve damage" from slouching over laptop screens.

ENGADGET: Laptops are dangerous / not dangerous: back pain edition

But the rationale for spares is a corollary of Murphy's Law: Batteries run down precisely when you need them most.

FORBES: Spare Batteries