I have sometimes wondered: if a tablet or laptop is plugged in, does the power used come via the battery or directly from the plug?
I’m using a great keyboard now, which is not avaliable in a wireless version. So I have it plugged into my iPad Pro via a USB-Lightning adapter. I’ve had power plugged into the adapter, but last night I unplugged it to give the battery its monthly exercise. And almost all the iPad’s power drained overnight, though it was sleeping. Surely most of it went to the backlighting of the keyboard, but still.
Of course when I have it plugged in, the power use is not costly, but if the power drain goes via the iPad’s battery, then the battery’s lifespan may be shortened noticeably by all the extra draining and charging…
Can anybody enlighten me?