50000mAh Power Bank Dual USB Outputs for $15.99 at walmart
From what I understand, it’s more or less like that. The faster a battery is discharged, its capacity decreases.
Charging the battery also has its characteristics and does not take place in the entire range with the same parameter.
I have some doubts about these numbers in practice outside of marketing. 
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So, C is a unit representing the discharge rate that would theoretically discharge the rated total battery capacity in one hour?
I am having trouble understanding this both in your comment and @rcxb’s graph.
Yes.
C-rate graphs are describing discharge behavior of Lithium ion cells.
That’s a couple of steps away from the discharge behavior of your power bank. Because from the battery cell output to power bank output, there is conversion circuitry, and we’re actually talking about DIFFERENT voltages. Its efficiency also counts.
Worse yet. You don’t know what exact type or model of Lithium cells a power bank vendor would use. Even with teardown, usually can’t tell much from the markings. So basically consumers count on the claim made by reputable manufacturers.
Not all Lithium cells are equal. Brand name cells (e.g. Xiaomi says they use LG/Panasonic cells) usually have > 90% usable capacity of advertised capacity. However, without any qualifiers in their specs or marketing material, that > 90% usually means discharge at 5V 1A (the basic use by today’s standard).
When you discharge these power banks at higher current (meaning charging your devices at higher current), the usable capacity (for a single discharge cycle) is usually lower than what you could achieve at 5V 1A. And this. The reason behind it is kind of connected back to the C-rate graph.
“30% - 80%” or “20% - 80%” rules are urban myths.
Personally I don’t believe such “rule of thumb”. Again, I think it originated from Lithium cell charts of chemical/physical properties. But then people in the old days wishfully equate the percentage to what your devices report and display. I love to be proved wrong on this one as years ago I tried to find some supporting evidence but I couldn’t.
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I don’t know exactly what part of it you disagree with and something tells me no amount of internet sources would change your mind. I haven’t done any clinical trials, but my experience with used cells across a few thousand miles and no discernible degradation using those methods seems to be a different experience than that of other people on their ebikes, including name brand models. I don’t have anything to share but my limited experience, although hopefully in the future I can take and record better measurements to share.
it’s rare for people to pull a pack apart and see if a BMS died, a cell died, some sort of corrosion issue (this is how I snagged an electric fat bike for only $350) or if they degraded the entire pack mostly evenly. Without pulling things apart and inspecting everything thoroughly, it’s hard to tell what happened when a pack goes bad, and this can happen even when people try to take good care of their stuff.
I did have one pack with a BMS that only does a top balance, and the charger was shutting down before it would balance. Compounding that with not fully charging every time and a few cells drifted enough to cut my range by over 20%. I put a trickle charger on the low cell, and as it filled up, the BMS top balanced all of the cells and my range returned to normal. I thought for certain I would be rebuilding the pack, and eventually the one drifting cell will need replacement, but it’s been fine for now. I’d imagine other people may have similar experiences with range loss for various reasons and wouldn’t know how or risk attempting to do this. This also doesn’t prove anything about extending battery life, but at minimum it proves to me that I haven’t severely degraded that or any of my other packs, which seems pretty good to me for used cells.
It’s also an entirely different animal than a single cell or 1S unit. Most people replace their electronics more frequently than would make sense to spend a bunch of effort trying to baby a cell even if it does work. Worrying about getting 7+ years from something that will be replaced in half that time is wasted effort. I plan on having my fat bike live longer than I do, and with a bit of luck I won’t be replacing the battery too many times.
Was referring to Internet advice on how users should use and charge their Lithium battery to extend its useful time. The rule of thumb usually goes like this: charge your phone to 80% (not 100%) and stop; use your phone to 20% (not 0%) before recharging.
Little to none difference in extending battery’s lifespan vs charge it to 100% and use it down to 0% before recharge in my experience.
Anecdotes are not data. The fact that fully discharging Li-Ion (and several other chemistry) batteries causes damage and shortens their life is not a matter of debate. There are innumerable sources and plenty of explanations of the chemical reactions if you care to read:
I went through Lithium ion chemistry and properties years ago. I understand the stuff you pointed to. You have to come up with better insight in order to be convincing enough for me. As I said earlier people like you wishfully equated the percentages you read from those properties charts to the display your devices tell you.
Ask yourself: when your phone tells you 0% battery, is it really and fully depleted?
Anecdotal evidence, but I tried this on my Moto G4 since I bought it. I had it since 2016. Only about last year, in 2021 did it start to lose charge faster, with the same amount of use. When I got it, it lasted me for a week without charging. By 2020, it still lasted me 3 days. In 2021, it barely lasted 2 days with a SIM in it, so I have been using it without a SIM since. As a mini-tablet, with about the same amount of use as before, I still get about 3 days of charge now.
But since 2021, my phone started turning off at about 60% battery. Sometimes it can go lower, like 20% before it shuts off, if I am not using it. But if I am on a call, it can die anywhere between 40 and 57%, because the CPU and display draw too much current together. If the screen is off, it is usually fine.
I would expect the voltage on my battery to be very low after 6 years. I would really love to make this poor phone wall-only, like to make it work without a battery and just some wires going underneath the cover where the battery is.
I haven’t taken care of my current phone like it did with the G4, because I bought this in mind as a disposable phone (which it kinda is, it really doesn’t matter that much what happens to it). Now I just let both my phones to charge to 100%, only because my new one charges too fast, and my G4 needs to charge more before it can hold a decent amount of charge again.
On the contrary, if you believe phones are intentionally misrepresenting their battery state-of-charge, the onus is on you to provide some evidence to support that claim.
I think that the person is essentially going off this
you see 100% charge on your phone, that’s not actually 100% charge on the battery, and when you see 1-0% on the phone, that’s not 0% on the battery, in fact I believe with lithium batteries if you fully drain them they are dead dead as in no coming back.
I think what he is referring to is you have no real proof other than blind trust that your phone/tablet is actually changed what it says it is.
I mean, if phones were going for longevity and not wanting to deal with warranty issues because of user stupidity, it makes a lot of sense, samsung has a charge limit for 80% and for all I know that’s placebo, just like its not fast changing either.
I mean we know data on the actual tech, but we don’t know the data at all with how its implemented in phones till 16000-20000 hour long power cycle test on devices, that is roughly 2 years and and 2000 charge cycles, and at that point the data is irrelevant due to new devices coming out so who cares what the old ones did/behaved, new battery tech is in the new devices.