Woll wrote:Does anyone know how Mobile phones, cell phones know how much the charge is left in batteries?
Is it hardware built into the battery, or a software program?
I can't answer your question directly but...
The batteries I use have 5v regulators build in - that means it's not possible to monitor how 'full' they are outside the battery itself. The battery does have a set of LEDs showing the amount of charge left, and there is circuitry inside. So if you want to monitor charge level, you want the raw LiIon batteries and the regulator and a circuit between the battery and regulator measuring directly the voltage of the battery. 2 LiIon batteries (which is what's in my power bank) charge up to about 8.3V and discharge down to about 6V, so either an ADC measuring the voltage, or just a zener diode as a warning of some power threshold would do the job.