Getting the most charge out of your phone's battery

What's the best way to charge your cellphone?
Is it better to keep the battery as full as you can, or should you regularly run it all the way down to zero before you charge up?
According to Apple, an iPhone uses fast charging until a battery reaches 80 percent, then it switches to a trickle charge for the last 20 percent.
Faster charging is more convenient for the user, but slower charging is better for battery longevity. The company further states that lithium-ion batteries work in "charge cycles."

You use up one charge cycle when you discharge 100 percent of a battery's power. That can mean taking a 100 percent full battery and running it down to zero. One charge cycle can also be consumed by using 75 percent of your battery power one day, then recharging overnight and using 25 percent the next day. Those two days' power draw will equal one charge cycle. Apple says its batteries should still have 80% of their original capacity after 500 charge cycles.
So what can you do to increase the lifespan of your battery? For starters, don't let the phone get too hot or too cold. The iPhone's lithium-ion batteries behave best between 32 and 95 degrees.
If you keep your iPhone in a protective case and notice that your phone gets hot when you charge it, remove it from the case while charging.
If you have a Samsung phone, the company advises users to try not to let the phone's battery level drop below 20 percent and to avoid completely draining it to zero.
The sweet spot for battery health seems to be keeping it between 80 percent and 20 percent charged.
Both Apple and Samsung recommend keeping the battery at a 50 percent charge if you are storing the phone for extended periods. The battery will drain itself over time, even when powered off.
It's best to check a stored phone every few months and bring its charge back up to 50 percent.
If you begin to notice strange battery activity, like shutting off when there is still 10 percent or 20 percent of the charge left, it's probably time for a new battery.
You can check your iPhone or Android phone's battery health through the battery control panel inside Settings.
A good idea is to charge your phone overnight so that you start each day at 100 percent. Of course, best practices and real life don't always mesh.
If you're going to be out late, try to top off before leaving so that you can keep the charge level above 20 percent at the end of the day.