I've always been told that letting my device battery die completely, powering off, then plugging in to charge was the best way to not burn out your battery. Recently it seems it's been affecting the battery itself, and charge lasting less and less. What would be the smartest way to charge iPhone?
iPhone 7, iOS 10.2.1
Charge it when you want to, for as long as you want to. You should not let a Lithium chemistry battery fully discharge; it shortens its life and can even kill it. Fortunately, iOS will not allow the battery to fully discharge. When it reaches zero the phone will shut off, but that "zero" is not fully discharged; there's a built-in safety factor, so if you let it go to zero then charge it immediately it won't do any harm. But there's no benefit either. What you should never do is let it go to zero, then leave it uncharged for a long time (more than a day or two). This will shorten the battery life. See my battery tip here: When to charge your iPhone or iPad
Charge it when you want to, for as long as you want to. You should not let a Lithium chemistry battery fully discharge; it shortens its life and can even kill it. Fortunately, iOS will not allow the battery to fully discharge. When it reaches zero the phone will shut off, but that "zero" is not fully discharged; there's a built-in safety factor, so if you let it go to zero then charge it immediately it won't do any harm. But there's no benefit either. What you should never do is let it go to zero, then leave it uncharged for a long time (more than a day or two). This will shorten the battery life. See my battery tip here: When to charge your iPhone or iPad
It's not necessary or recommended to do that. Charge it when it is convenient to do so, regardless of the %age. See the following from http://www.apple.com/batteries/why-lithium-ion/
Charge your Apple lithium-ion battery whenever you want. There’s no need to let it discharge 100% before recharging.
Deep discharge cycles degrade lithium cells faster than shallow cycles do. It's one if the reason all industry standard SMART lithium batteries shut down the device before the battery is fully discharged as a true 100% discharge can dangerously damage a lithium cell.
What you've been told as an optimal practice made sense 15-20 or more years ago with the then commonly used NiMH batteries. It has never applied at all to lithium batteries.
I suggest you never let your battery completely discharge.
Lithium batteries like to be used at all times whether its being drained or charged. Letting the battery set for extended periods of time will also degrade the battery. If the battery is going to be sitting for a long period of time its recommended that you have it plugged into the charger.
Also, the batteries in modern smartphones are SMART and will via software shutdown the device once 20% life has been reached, it is possible to squeeze more life out of it but once the phone reaches 10-5% life the device will not fully boot up any longer until it is charged.
Is it bad or good for one to let iPhone battery fully die before charging again
