What is the electrical reason some devices like mobile phones require a working battery even during times when they are plugged into a wall?

Question

If the battery fails on a mobile phone, why is it unusable even when it’s plugged in to the wall?
There are many older electrical gadgets that can work with either batteries or being plugged in. Take an old fashioned alarm clock or stereo. If there’s no batteries in it, and you plug it into the wall it will work. If you unplug it, it won’t work unless there are good batteries in it that are charged. So why can’t a mobile phone work when plugged into the wall when the battery has failed?

In: 18

Answer 1

This is kind of device dependent. I know there are some android devices that actually require more power than it’s charging circuitry can provide when under load. This is especially true of cheap phones, where they will only charge if sitting there with the screen off and not being used. Also, most phones require a charged battery when doing software updates as a failsafe since the phone shutting off while updating can cause it to stop working.