The best way to charge your phone is a little at a time, whenever you have a chance.
Don't fully discharge your phone before plugging it in.
Battery University says that so-called deep discharges – which happen when you use your phone until only a small portion of its battery life is left — wear down batteries.
It's clearly impractical to always keep your phone charge between those levels, but at least you know what's ideal!
If you can't do that, shoot for keeping its charge level between 45% and 75%.
The second best charge range for batteries inside smartphones is between 45% and 75%. That's probably a lot more realistic for most people on a day-to-day basis.
But you do have some wiggle room. If you typically keep your phone's charge level between 25% and 75%, you likely won't cause too much long-term damage.
Never fully charge your battery — and particularly not from a low charge level.
In fact, charging from pretty much any amount to 100% is a bad idea. According to Battery University, lithium-ion batteries do "not need to be fully charged, nor is it desirable to do so. In fact, it is better not to fully charge, because a high voltage stresses the battery" and wears it out in the long run.
You likely shouldn't charge your phone overnight.
I've seen a lot of debate about the effects of charging your smartphone overnight. But if charging to 100% causes the most damage to a phone battery's lifespan, you should probably cut it out.