IPad shows it's fully charged at 90%

Question

When I charge my iPad, once it hits about 90%, the battery icon changes to plug, means "Fully Charged". After leaving the iPad plugged in for about one hour it eventually reaches 100% charge.
My question is, why does the iPad show it is fully charged when only at 90%?
Thanks!

Answer 1

drsailer wrote:
Michael,
If I'm not mistaken, charge cycle on an iPad is the same as on a Mac portable computer. 1 charge cycle = 100% discharge. So, 92-100 would only be 8% of a charge cycle. If you charge your iPad from 50% to 100% on 2 separate days, that is only 1 charge cycle, not 2.
You're correct, and I'm remiss in using the same term as Apple does in their literature (which, btw, is pretty good on this topic) without it meaning the same thing to me. I should instead be saying something like charging actions, I.e., the simple matter of plugging in and charging up.
Nominal battery life for the iPad is set at 1000 cycles, as you correctly defined it. Conditions and patterns of use, however, will have an effect on that number. All else being equal, battery life will be reduced when operating at higher temperatures. Batteries which are not stored for long lengths of time before entering into use will have longer lives than those which are.
Another characteristic of these batts are the deposits which build up inside each time a charging current is applied. You can't avoid this happening, it's the main driver of battery life, and .... most significant of all, to me at least .. the fact that the heaviest or quickest buildup of these deposits takes place right at the start of each charging action.
The question then, is whether there is any downside to having multiple charging actions every day, as in perhaps plugging it into a charger whenever it's not in use. My own answer to that is yes, it will have one. How significant? Don't know, and no way to tell without running some long, boring trials. All I can say is that, for me, the advantages in avoiding that pattern of use are obvious enough, even while admitting we are still years away of being able to know if battery life is going to bs the main driver in EOL decisions on our happy little machines.
I agree, though, on the exact battery readout. I was just trying to explain the behavior. And the indicators are notoriously inaccurate.
And will become more so, per Apple and other guidance, if you omit the "monthly run it to empty".