iPad shows it's fully charged at 90%

From my understanding of what I've read and seen, the iPad charges very rapidly to 90%, then enters a slower rate of charging, which is a bit more than a trickle. So, it will eventually get to 100% after time, but the rapid charging segment is finished at 90%.

The same thing happens to iPods and iPhones, but they don't show the change in the indicator. iPods and iPhones rapidly charge to 80%, and then drop to a slower charge rate to get to 100%.

Larzuk wrote:
.. My question is, why does the iPad show it is fully charged when only at 90%?

My best answer, and the only one where you can actually do anything about it, is that you haven't been following Apple's advice to run your battery completely down once a month, to the point where the iPad shuts down, and then follow that with a full charge. Failure to do so will affect your battery's "gas gauge" and what you're seeing will happen.

Michael,

I do run mine down once per month, and both my iPad and my daughter's show the same behavior - they have since day 1. Most people don't notice, as they plug it in at night and then see the 100% the next morning. Try plugging in your iPad when it's at 92%. It will probably show charging for a bit, but then show fully charged before reaching 100%, although it will climb to 100% eventually.

Well, you're right, that's something that I'd never see. As battery life in Li-ion types is limited by charge cycles, and as running up from 92 to 100% would be a cycle, I work at only putting it on the charger once per day.

On the one hand, you seem to be describing your effect as normal operation, albeit one that most would never notice. OTOH, just how important is an exact readout of battery power levels when in the top 8% of the range?

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.

I agree, though, on the exact battery readout. I was just trying to explain the behavior. And the indicators are notoriously inaccurate.

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".