[Android Apps and Games] Jollyriffic:
lithium batteries at 100% aren't at the max capacity that they can actually charge up to. so 100% doesn't harm the battery.

They are listed as 3.7v, full charge = 4.2v. However with a higher voltage you could charge it higher, i know, because i've tested it with 26650, 18650, 14500, and 10440 (also some half height 3.7v and 3.0v cells), bag cells, and i think also one of those cr23x sort of larger flat round cells.

When testing charge capacity % to %, the only factor that kills a batteries longevity is letting them dip down to 20% battery life. Really at 25-30% you should be shutting off the device.

if you constantly keep charging it up to max, example 50% then charge to 100% you'll get about 9x the longevity out of the cell.

Now if you try hunting down the 80% data, there's text about it, claims about it, but no statistical data.

i also don't have data, because cells aren't my livelihood. I use them a lot, i have a lot of cells, for different electronics i build.

so real world, you don't want to hit 20%, anytime you can charge, do so regardless of % battery life.

The misinformation about 80% was the fact that when you get a cell, they aren't fully charged, but that's just a safety measure should the cells crack/exposure, it will have less energy to dissipate. also that's more money they would be paying per cell to charge to max, think about that, millions of batteries, the pennies that power takes hits your profit margins. The second part of the theories basis, is that a "cycle" for charge, is considered complete at 80%. meaning that when it's depleted (say 20%), charging to upto 80% "at least" = 1 full charge cycle., however 90% or 100% is still also 1 cycle. This is basically just leaping to conclusions since that 80% was mentioned about cycles.

charge cycle is important, as it gives you a potential range to say "ok i've charged it this many times, so it's replacement time". this isn't really a normal users guideline, it's for places like hospitals that use battery backup in their machines, or other industries that have to meet compliance with regulations. This specifically is how many people in the DIY Powerwall groups/forums get their 18650 batteries to DIY their own. You'll test each cell, then group them by mAh rating, use the best, and maybe sell or dispose of them correctly.

this lead to the "theory" that this prolongs the life, when the reality is, letting the voltage go low is the only part of % that kills them.

The other killer, most people don't even know about, is fast charging.

that's fine for something like wireless charging, as you're losing a good deal of wattage in the transfer from 6.78 MHz transmission to magnetic coil.

slow charging is the best way to charge lithium.

I've done those tests also, have a bench setup with cycling cells, using different voltages, amps, etc.

more wattage you throw at charging, the worst it is for the cell.

there's easy solutions, to prolong the battery life.

when you sleep, throw it on something 0.5 amp charger.

If you need to charge up quickly, i wouldn't exceed 2amp 5v, over usb.

as for wireless, i did some tests, was pretty efficient at killing a "good" cell phone battery at 9v 2.666 amp, and 12v 2amp.

Using anything over 6v 3amp on usb, really quick to kill the battery also. On wireless that seemed fine, but usually opted for 5v 2amp for wireless.

Testing for this was mostly done on a nearly new, droid turbo 2, and a samsung note 2 battery.

the note 2 is not a quick or wireless charging phone, but the battery can be tested easy as you can just run them as is on a bench.