Why do my devices that use lithium batteries often still perform well even at a low charge?



Versus say, almost dead AA’s in a toy.

In: Chemistry

Lithium batteries have some circuitry in them that shuts off the battery to protect it. If they are discharged too low it can damage it. Double As are pretty dumb in but you get to squeeze out every bit of juice out of them without much worry

A battery’s voltage will slowly drop as it discharges.

For something simple like a toy the circuit is probably just a motor, speaker, and/or a light, these things will carry on running on lower voltages (to a point) but they will get less powerful.

For something like a laptop or a phone, they have to have a consistent voltage to work properly (e.g. 12v). The battery’s voltage will still drop as it is used, but there is some clever circuitry that converts this dropping voltage into a constant one. This means that the device doesn’t care that the voltage has dropped until so much of the energy in the battery has been used that we can’t convert it to what we want any more, at which point the device will turn off rather than potentially damage itself with the lower voltages.