How do things tell how much battery life is left?

Question

I have a wireless mouse and keyboard and they have a battery meter (for alkaline batteries) and I was wondering how it knows how much battery life it has? Does it do it based on time? Same thing for my iPod and cell phone (built in rechargeable)? Same way? Thanks.

Answer 1

Most battery types have a very distinct way that they discharge, so using that information, the item can estimate how much time remains in the battery by sensing the voltage and/or current that the battery is presently producing.

I'm sure that you've found by now that it is only an estimate and that sometimes it's not quite right on...