Should you drop your iPhone battery to 0 Percent? No

Running a smartphone until it's dead—a full discharge—every time is not the way to go with modern Lithium-ion batteries. Don't even let it get that close to 0 percent. That wears out a Lithium-ion battery even faster than normal. Partial discharge is the way to go.

Batteries are on borrowed time from the get-go. The insides are in a state of decay that can't be helped. Over time, they're simply going to hold less and less power. If you've got an old iPhone 5 or 6 still in use and wonder why it's only got a charge for a few hours compared to the almost full day you got when it was new, that's why. The capacity diminishes over time.

The only time you would want to go out of your way to drain a smartphone battery to zero is to recalibrate the internal sensor that displays your phone's battery level. It's hardly guaranteed—in fact, many people don't think it works at all—but it's recommended by some, especially if you've got a phone that hits 10 percent (or even 20 or 30 percent) and seems to abruptly die.

Even if you do use the phone all the way to auto-shutdown, that may not mean the battery is at 0 percent. Leave the phone be for a few hours, if you believe this is worth doing. Then give it a reset (holding down the Home and sleep/wake button simultaneously) for good measure.

Best Thing to Do: Plug the phone in before it asks you to enter a low-power mode; iOS will ask you to turn that on when you hit 20 percent power. Plug it in when the phone is between 30 and 40 percent. Phones will get to 80 percent quickly if you're doing a fast charge. Pull the plug at 80 to 90, as going to full 100 percent when using a high-voltage charger can put some strain on the battery. Keep the phone battery charge between 30 and 80 percent to increase its lifespan.

Fast charging like we've seen in Android phones for a while finally arrived with the iPhone 8 and X. Before, it took an iPhone a couple of hours to go up 50 percent. Apple claims the 8 and up can increase 50 percent in only 30 minutes with the right chargers. That requires a USB-C power adapter, which in turn means owning a special USB-C-to-Lightning cable, neither of which are included with an iPhone; or using a higher voltage charger like the one from an iPad or even a MacBook.