Do cellphones use battery power when powered off?

Question

If I left my cellphone powered off overnight or for a week would the battery still have the same charge when I turned it back on?

There is an auto power off/on function or a full power off, does it make a difference to battery charge?

Answer 1

Everything makes a difference.    

Shut it off completely to increase the charge holding time.   

            

All batteries self-discharge, 

so it will go down at least a little bit over time no matter what.  

Answer 2

Lithium-ion batteries drain a very small amount even when they're sitting unused, which is why that old phone or whatever that's in your junk drawer doesn't turn on when you take it out a year later.

They average about 2-3% of self-discharge a month. So a phone with a healthy battery would maybe be a percent or two lower than when it was last turned on after week without use.

Answer 3

It should have the same charge if you power it off completely. 

If it’s on standby, you might lose all power after about a week.