Definitely don't do this. That is one of the worst thing you can do to a Lithium ion battery. It does nothing but harm your battery.
Up until somewhat recently, Apple recommended people do this monthly... Doesn't harm it as much as you'd think. Yes, draining a lithium ion to 0% with no voltage will destroy it, but the phone turns off way before this happens. A lot of people use their phones till it hits 0% and turns off - yes, this is more stress on the battery, but the WORST thing you can do is leave your phone in the hot sun (direct sunlight) for hours and hours, not run it down to 0%. ....
My wife runs her phone down to single digits all the time and her battery capacity (mAh) vs design capacity (mAh) is within 5% of mine and I use my phone mostly from 80-100%.
From Apple's own website:
Use iPhone Regularly
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).
Looks like they got rid of this in 2014? The archive website is horribly slow.
Not that I'd recommend it often, but it does help with battery % calibration.
I've had more than a few times where, after an iOS update, my battery drops 50% in less than an hour. This continues to happen even after reboots. I find running it down to 0%, the phone will last 5-6 hours at 6% and then finally die - recalibrating the battery % reader. As I stated in my original post, this usually only happens after a major iOS update for me.
It's pretty amazing people will believe a $1.99 app instead decades of academic and industrial research on lithium batteries.
Instead, people want to believe their battery with over 200 cycles hasn't aged a bit. LOL.
The app is reading data put out by the phone. Are you calling the own phone's stats incorrect? As posted on other threads in this forum, coconutBattery is far more accurate since iOS hides a lot of the data that it used to show pre-iOS 10.
Having actually worked with lithium ion batteries for awhile (they're a hobby of mine) - it's not uncommon for mAh capacity to be near or close to design mAh capacity after 1-2 years of usage with care... Most cheap batteries drop very fast, but if you get high end Panasonic or similar cells - they can be close to 100% even after years of usage. Otherwise Tesla cars wouldn't last more than a few years...
My boss had an old iPhone 4s with thousands of cycles on it - still using it for his daily phone up until a few months ago. These batteries are pretty resilient if you take care of them.
The guy who did this website (Isidor Buchmann) writes a great book about batteries - https://www.amazon.com/Batteries-Po...id=1499300150&sr=8-1&keywords=isidor+buchmann
As you can see, for the 1-2C discharges, the capacity stays about the same. http://batteryuniversity.com/learn/article/bu_808b_what_causes_li_ion_to_die
So has a battery after 200 cycles aged? Yes. Has it lost capacity? For some, maybe not a lot depending on how it was abused/used.
But you guys both have good advice for battery longevity: Charge slow, don't run down past 40% if you can help it, and avoid heat.