how does my cellphone stores the energy it gets while charging and use it economically for about 3 days?

Answer 1

hey man, never heard about lithium batteries ?

here there is a link with all the infos you want.
http://en.wikipedia.org/wiki/Lithium_battery

simply the battery will absorb a lot of watt/hour in a short time when you are chargin it from a power supply, and the phone will take little watt/hour and the battery will last a few days.

I have a solar power supply for my phone.

it took 2.5 hours t charge it from the power line.
8 hours to charge it from the solar panel, because the panel producce less energy the power line, so it need more hours to recharge completely.
my battery last for 5 days.

Answer 2

Most cellphones use a lithium ion battery. Like pretty much all batteries, they store energy in chemical bonds and release it as needed. A cell phone sitting around doesn't really draw a lot of power (compared to something that actually produces heat or lots of light or does work), so a relatively modest charge will do you for a few days usually.