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

among other things, the battery is functionally a voltage converter.

the electricity going into the phone is 5 volts, which is fine for charging the battery, but the battery discharges at 3 or 4 volts into the computer.

there are voltage changing circuits for DC voltages that don’t require a battery (there’s a giant one in your microwave) but it’s a lot of unnecessary work.