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[INFO] Li-ion batteries myth busting

Updated and simplified version here : http://forum.xda-developers.com/showthread.php?p=3846897#post3846897
I've been around this forum for some time now and I have noticed one thing that is spelled in all sub-forums: BATTERY LIFE
So I thought of pulling some info together that is relevant to our Raphs (Li-ion batteries), taken from www.batteryuniversity.com.
Hope you find it helpful and understand better behaviour of your battery
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About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC.
Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world.
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"If possible, do not discharge lithium-based batteries too deeply. Instead, recharge more often."
Lithium-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge is less than half compared to nickel-cadmium, making lithium-ion well suited for modern fuel gauge applications.
Lithium-ion has not yet fully matured and is being improved continuously. New metal and chemical combinations are being tried every six months to increase energy density and prolong service life. The improvements in longevity after each change will not be known for a few years.
Charging
There is only one way to charge lithium-based batteries. The so-called 'miracle chargers', which claim to restore and prolong batteries, do not exist for lithium chemistries. Neither does super-fast charging apply. Manufacturers of lithium-ion cells have very strict guidelines in charge procedures and the pack should be charged as per the manufacturers "typical" charge technique.
Lithium-ion is a very clean system and does not need priming as nickel-based batteries do. The 1st charge is no different to the 5th or the 50th charge. Stickers instructing to charge the battery for 8 hours or more for the first time may be a leftover from the nickel battery days.
Most cells are charged to 4.20 volts with a tolerance of +/?0.05V/cell. Charging only to 4.10V reduced the capacity by 10% but provides a longer service life. Newer cell are capable of delivering a good cycle count with a charge to 4.20 volts per cell.
A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.
Batteries live longer if treated in a gentle manner. High charge voltages, excessive charge rate and extreme load conditions have a negative effect on battery life. The longevity is often a direct result of the environmental stresses applied. The following guidelines suggest ways to prolong battery life.
The time at which the battery stays at 4.20/cell should be as short as possible. Prolonged high voltage promotes corrosion, especially at elevated temperatures. Spinel is less sensitive to high voltage.
The lower charge current reduces the time in which the cell resides at 4.20V. A 0.5C charge only adds marginally to the charge time over 1C because the topping charge will be shorter. A high current charge tends to push the voltage into voltage limit prematurely.
Do not discharge lithium-ion too deeply. Instead, charge it frequently. Lithium-ion does not have memory problems like nickel-cadmium batteries. No deep discharges are needed for conditioning.
Do not charge lithium-ion at or below freezing temperature. Although accepting charge, an irreversible plating of metallic lithium will occur that compromises the safety of the pack.
Not only does a lithium-ion battery live longer with a slower charge rate; moderate discharge rates also helps.
Discharge of the lithium-ion battery is 5% in the first 24 hours after charge, and then reduces to 1% to 2% per month thereafter. The safety circuit adds about 3%. High cycle count and aging have little effect on the self-discharge of lithium-based batteries.
The battery industry is making incremental capacity gains of 8-10% per year. This trend is expected to continue. This, however, is a far cry from Moore's Law that specifies a doubling of transistors on a chip every 18 to 24 months. Translating this increase to a battery would mean a doubling of capacity every two years. Instead of two years, lithium-ion has doubled its energy capacity in 10 years.
Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate.
Despite its overall advantages, lithium-ion has its drawbacks. It is fragile and requires a protection circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge. In addition, the cell temperature is monitored to prevent temperature extremes. The maximum charge and discharge current on most packs are is limited to between 1C and 2C. With these precautions in place, the possibility of metallic lithium plating occurring due to overcharge is virtually eliminated.
The worst condition is keeping a fully charged battery at elevated temperatures, which is the case with running laptop batteries. If used on main power, the battery inside a laptop will only last for 12-18 months. I must hasten to explain that the pack does not die suddenly but begins with reduced run-times.
The voltage level to which the cells are charged also plays an important role to longevity. For safety reasons, most lithium-ion cannot exceed 4.20 volts per cell. While a higher voltage boosts capacity, the disadvantage is lower cycle life.
"how deep can a battery be discharged and still achieve maximum service life?" There are no definite answers. Batteries are like us humans. Suppose we ate all the vegetables our mother heaped on our plates and do our daily exercise, would we life longer? Perhaps. But by how much, no one will know. Batteries lose capacity as part of aging, cycling and exposure to heat. Nickel-cadmium also loses capacity due to lack of exercise because of memory.
Some lithium-ion batteries fail due to excessive low discharge. If discharged below 2.5 volts per cell, the internal safety circuit opens and the battery appears dead.
Aging is a concern with most lithium-ion batteries and many manufacturers remain silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not.
Lithium-ion batteries lose capacity through cell oxidation, a process that occurs naturally during use and aging. The typical life span of lithium-ion is 2-3 years under normal use. Cool storage a 40% charge minimizes aging. An aged lithium-ion cannot be restored with cycling.
Shorted Cells
Cell reversal caused by deep discharging also contributes to shorted cells.Specified to deliver 100% capacity when new, the battery should be replaced when the capacity drops to below 80% of the nominal rating.
The self-discharge on all battery chemistries increase at higher temperatures. Typically, the rate doubles with every 10°C (18°F). A noticeable energy loss occurs if a battery is left in a hot vehicle.
Premature voltage cut-off
Not all stored battery power can be fully utilized. Some equipment cuts off before the designated end-of-discharge voltage is reached and precious battery energy remains unused. Applications demanding high current bursts push the battery voltage to an early cut-off. This is especially visible on batteries with elevated internal resistance. The voltage recovers when the load is removed and the battery appears normal. Discharging such a battery on a moderate load with a battery analyzer to the respective end-of-discharge threshold will sometimes produce residual capacity readings of 30% and higher.

Counterfeit cell phone batteries (clone batteries)
In the search for low-cost battery replacements, consumers may inadvertently purchase clone cell phone batteries that do not include an approved protection circuit. Lithium-ion packs require a protection circuit to shut off the power source if the charger malfunctions and keep on charging, or if the pack is put under undue stress (electrical short). Overheating and 'venting with flame' can be the result of such strain.
Cell phone manufacturers strongly advise customers to replace the battery with an approved brand. Failing to do so may void the warranty. Counterfeit cell phone batteries have become visible since the beginning of 2003 when the world was being flooded with cheap replacement batteries from Asia.
Cell phone manufacturers act out of genuine concern for safety rather than using scare tactics to persuade customers to buy their own accessories. They do not object to third party suppliers in offering batteries and chargers as long as the products are well built, safe and functioning. The buyer can often not distinguish between an original and a counterfeit battery because the label may appear bona fide.
Caution should also be exercised in purchasing counterfeit chargers. Some units do not terminate the battery correctly and rely on the battery's internal protection circuit to cut off the power when fully charged. Precise full-charge termination and a working protection circuit are needed for the safe use of the lithium-ion battery.
A large number of lithium-ion batteries for cell phones are being discarded under the warranty return policy. Some failed batteries are sent to service centers or the manufacturer, where they are refurbished. Studies show that 80%-90% of the returned batteries can be repaired and returned to service.
© Copyright 2003 - 2005 Isidor Buchmann

Great thread! Wiki!

Thanks
Tis is good info to know and to share. Thanks for putting this together for us all.

overcharging Fuze battery
When I exchanged my Fuze for a new one at AT&T, the service person said my battery was bad, due to overcharging. She said leaving my Fuze plugged into my car charger and my computer(with charging turned on) degraded the battery.
There is an option to NOT charge the battery when connected by USB to the computer.(kind of indicates no automatic charging control)
Well, I use my Fuze as a computer 12-14 hours a day. I want to see the screen, which means I need it plugged in either to the computer or car charger.
If I turn off recharging when connected to my computer, I end up with a dead battery pretty quickly, since I use it a lot as my business phone with a Bluetooth speakerphone.
The AT&T person said this information was given to them by HTC.

Thank you for the infos. Really need this cause battery life is my main concern.

recharge cycles
from reading other posts, it looks like the batteries have around 1000 recharge cycles.
Unfortunately, the cycles can occur every time you plug into your computer or charger, even if the charge goes from 99 to 100 %.
Which means I need a new battery probably every 9-12 months. Not too bad.

hrothnir said:
When I exchanged my Fuze for a new one at AT&T, the service person said my battery was bad, due to overcharging. She said leaving my Fuze plugged into my car charger and my computer(with charging turned on) degraded the battery.
There is an option to NOT charge the battery when connected by USB to the computer.(kind of indicates no automatic charging control)
Well, I use my Fuze as a computer 12-14 hours a day. I want to see the screen, which means I need it plugged in either to the computer or car charger.
If I turn off recharging when connected to my computer, I end up with a dead battery pretty quickly, since I use it a lot as my business phone with a Bluetooth speakerphone.
The AT&T person said this information was given to them by HTC.
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Which tells you how much you should listen to most AT&T people about technical issues and details. They were 100% wrong about the impact of charging continuously. And unless they were talking to an HTC hardware engineer...
It's more likely that your issues were simply caused by heavy use, which will cause any rechargeable battery to wear out more quickly. Most batteries I've seen will last between 500-1000 charging cycles, so if you're a heavy user and are wearing down your battery frequently, you'll "run through" those charging cycles more quickly.
The advice you were given is worth ignoring.

does it make any difference
Does it make any difference if i charge my fuze from a
- charger connected to power outlet
or
- an USB cable connected to compute
Obviously, the USB option takes longer time to charge completely.
I wanted to know, which is suggested?

hrothnir said:
from reading other posts, it looks like the batteries have around 1000 recharge cycles.
Unfortunately, the cycles can occur every time you plug into your computer or charger, even if the charge goes from 99 to 100 %.
Which means I need a new battery probably every 9-12 months. Not too bad.
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Charging from 99-100% definitely will not qualify as "One" cycle. Discharging from 100% to some 20% and then charging up may count as one cycle. Similarly, 5 or 6 shallow discharging and charging 60%-40%-60% can count as one cycle. It is much better for battery health though. charging momentarily for one or two minutes which increases the battery percentage by 2-3% will not count as a full cycle.

Discharging ("deep-cycling") your battery? STOP doing that.

If you like to deep-cycle (fully drain/recharge) their battery, you should stop doing that. Many of us got used to deep-cycling the Ni-Cd batteries, and didn't notice the smooth transition to Li-Ion batteries.
In fact, I can't think of a phone (or any other gadget) that would use Ni-Cd battery today. AFAIK, all modern phones/PDAs have Li-Ion batteries (including Raphael) which you SHOULD NOT fully discharge.
Here's a quote from wikipedia.org (http://en.wikipedia.org/wiki/Li-ion_battery):
Like many rechargeable batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a long time, they should be brought to a charge level of around 40%–60%
Lithium-ion batteries should not be frequently discharged fully and recharged ("deep-cycled"), but this may be necessary after about every 30th recharge to recalibrate any electronic charge monitor (e.g. a battery meter). This allows the monitoring electronics to more accurately estimate battery charge.[27] This has nothing to do with the memory effect.
Li-ion batteries should never be depleted to below their minimum voltage, 2.4 V to 3.0 V per cell.
Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
Li-ion batteries should not be frozen [50] (most lithium-ion battery electrolytes freeze at approximately −40 °C; however, this is much colder than the lowest temperature reached by household freezers).
Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured.[27]
When using a notebook computer running from fixed line power over extended periods, consider removing the battery[51] and storing it in a cool place so that it is not affected by the heat produced by the computer.
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Hope this helps someone.

Is it true charging li-ion no more than 80% increase its life?

From http://www.wmskins.com/blog/how-to-increase-battery-life-of-windows-mobiles:
1. A Lithium Ion battery should never be charged to 100% or fully Discharged. The famous 80-20 rule is applicable here as well, though in a different way. Charging to 80% increases battery life.
2. Don’t wait for full discharge, charge it frequently. Keeping the battery near to 80% always, gives better life. This is also what many vendors claim as “memory effect”.
I followed that advice and then after a few weeks, when once I charged it to 100%, it dropped quickly to 80%! and has been like that since. now I don't give a damn to that rule and charge my phone to 100% instead.

At this point, I would advise you do a full charge and deep discharge of your phone. Just to allow the phone to calibrate itself to the battery again.
However, I would advise against running programs to intentionally drain it at a high draw. So instead of playing 5 hours of FPSECE to drain it flat, just let it sit on standby and use it as you normally would, until it dies. Then charge it back up in one continuous charge (refrain from unplugging until it goes back to 100%). Hopefully that will restore the accuracy of your battery meter by a bit.
And IMHO, the article you included discusses things about batteries that are no longer true....
2. Don’t wait for full discharge, charge it frequently. Keeping the battery near to 80% always, gives better life. This is also what many vendors claim as “memory effect”.
No. "Memory effect" is, in laymen terms, the battery not being able to hold above a certain charge after being repeatedly discharged from the same capacity. E.g. being discharged at 80%. It doesn't "give battery life" -- in fact it kills your battery's capacity.
This is a term more relevant for old NiCd batteries. LiONs and most NiMH batteries have very weak/no memory effect.
3. Every battery has limited Full charge-discharge cycles. Of the order of 300+. In other words a typical phone battery can be fully charged/discharged 300 times. Doing more frequent charges, as specified in point #2, will increase overall life.
Partially true. Every battery can be charged a number of times before its ability to hold a charge deteriorates. Usually this is around 300, though the exact number varies between individual batteries. However, the concept of a "cycle" isn't exact -- just because you charged from 60-80% (or whatever) doesn't mean you didn't use a cycle. It's really a continuum, and should only be conceptualized as the battery losing its ability to be charged and hold a charge, the more times you charge it.
4. During first time use (when the battery is new) don`t use it till its fully charged. This is why it is always written on manuals “let the device charge for 2-3 hours”.
The necessity of preconditioning is controversial now. There is little evidence to suggest that devices nowadays benefit from preconditioning, and likewise there is little evidence that not doing so harms battery longevity. Many manuals these days simply omit to mention preconditioning.
5. Best way to increase battery life is Not to use it. If you keep AC power plugged in on your phones, keeping the battery at 80% (as in #1), your battery will last longer. Though discharging it once in a month would be must in such cases.
Partially true. Not using your battery does indeed help its longevity, but not by plugging into the AC. Heat is a LiON battery's enemy, and plugging it into your wall will generate heat that is ultimately bad. This translates to laptop batteries as well -- if you want to store a laptop battery, the best bet is to discharge it to 40%, then put it somewhere cool (even the fridge if you want).
Also I would say doing a deep discharge once a month is too frequent. Once every 2 or even 3 months is more appropriate.
Finally, LiON batteries themselves have a shelf life. So even if you let them sit there, they will lose their function after a few years. Just so yo uknow.
6. Surrounding temperature contributes a lot. Colder weather gives better battery life. So make sure your cellphone doesn’t overheat, if it does, find ways to keep it cool.
True. And that's why you shouldn't leave it plugged in.
Learn more about batteries here: http://www.batteryuniversity.com/

felixdd said:
E.g. being discharged at 80%. It doesn't "give battery life" -- in fact it kills your battery's capacity.
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is that so? why? so i guess now my battery's capacity has lessened. damn the article.
have drained my battery to 1% and charged it to 100%. let's see how it goes from here..

good subject for discusion. WM user or not the battery life and the tricks of LION only a few knows.
1.i have two batteries for my HTC. he original battery and one with 2800mAh. Does my phone cofused if i change tha batteries aternately?
2. if ai want to work with my phone for hours is it better to connect it with the charger?
3. Wich kind of charging is better? with USB cable from pc or wall charger.

I have the option in my BIOS for my laptop which says an 80% charge will prolong the lifespan of the battery.
Batteries must undergo a fair bit of research (for environmental impact reasons if nothing else!) and to have such a bold statement to me indicates that its an obvious fact to battery researchers.
Given ive lay in bed this morning messing about on facebook and setting up rss feeds on my phone and emptied a full battery I dont think Id ever stop charging at 80%. Ill just buy another battery!

i really doubt cold weather improves battery life, numerous times my family and I brought electronic products to cold countries and the Battery life always drops at a much quicker rate

dan138zig said:
is that so? why? so i guess now my battery's capacity has lessened. damn the article.
have drained my battery to 1% and charged it to 100%. let's see how it goes from here..
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You are taking what i said out of context.
What I'm saying is that IF your battery had a memory effect as the original article claimed, then charging the battery to only 80 will create a memory at 80, which would be worse for your battery. I'm merely trying to point out an inconsistency in there article.
However, I went on to say that li ON batteries do not have a memory effect. So more relevant to the real world is the fact that our batteries will not experience memory as claimed by the article.

Two main things kill lithium batteries, heat and time as they promote deposits forming in the electrolyte, which reduces the capacity of the battery.
So, buying a "spare" battery at the time you buy a phone with a plan on using it when the original battery starts to fail is a bad idea as the spare battery would be slowly deterorating on the shelf.
Deep charges rather than top up charges are bad as they produce more heat inside the battery, although doing it if your battery doesn't seem to be holding it's chage is a good idea as it should recalibrate the phone's battery level software.

To paraphrase the old saying, " blogs and opinions are like a##holes, everyone has one "
I have followed the links in this thread and so far I have just read unsubstantiated opinion.
I have used " cordless " electronics for most of my life and have used all kinds of batteries extensively as well as talked to company reps and battery " experts ".
Nickel Cadmium batteries had memories. The batteries had to be conditioned and fully charged and discharged. The new Lithium Ion batteries were advantageous , not only because they held a bigger charge and lasted longer, but also because they have NO memory. The latest example being, I regularly charged my Tilt battery to all levels of charge. Mostly 100% everyday and ran it down to 5% most times before charging it again. I used it a lot and charged it a lot. and it lasted 2 yrs.
The only difference I have really noticed in batteries has nothing to do with the way you charge it. It has to do with " getting what you pay for " I have had quality batteries really show their quality and $ 12 batteries give me up to and only my $12 worth.

Charging Lithium Ion Batteries to 80%
denco7 said:
To paraphrase the old saying, " blogs and opinions are like a##holes, everyone has one "
I have followed the links in this thread and so far I have just read unsubstantiated opinion.
I have used " cordless " electronics for most of my life and have used all kinds of batteries extensively as well as talked to company reps and battery " experts ".
Nickel Cadmium batteries had memories. The batteries had to be conditioned and fully charged and discharged. The new Lithium Ion batteries were advantageous , not only because they held a bigger charge and lasted longer, but also because they have NO memory. The latest example being, I regularly charged my Tilt battery to all levels of charge. Mostly 100% everyday and ran it down to 5% most times before charging it again. I used it a lot and charged it a lot. and it lasted 2 yrs.
The only difference I have really noticed in batteries has nothing to do with the way you charge it. It has to do with " getting what you pay for " I have had quality batteries really show their quality and $ 12 batteries give me up to and only my $12 worth.
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I have a Nissan Leaf. It is clear that the engineers have spent a LOT of time thinking about how to maximize the life of the battery in the car. One of the options the car come with is to ALWAYS charge the batteries to 80%. In fact, they've gone as far as to add a button on the dashboard to override that setting in cases where a 100% charge is needed. According to the documentation that comes with the car, this is the single most important step to prolonging battery life. Next is frequent charges. Next is monitoring battery temperature which is constantly shown in a BIG display on the dashboard. In general, a good way to think about a lithium ion battery is that over its life you're trying to maximize the amount of power stored and then subsequently removed from the device. From the research I've done, if the "charging/discharging life" of the battery were cycles that swung from 100% to 0% you might get X kwHrs of power "moved" through the battery, yet if you were to limit charges to 80% and constantly charge it after each use, you could expect at least 2X! So it's a big deal. I live in Bellevue, Washington which has a very mild climate and have put 26,000 miles on this car in the last 2 years, making mostly small 3-to-20 mile trips, and I routinely charge the car when I pull into the garage, and would estimate that the battery has been charged well over 1000 times. To date, there is no detectable loss in battery capacity; the first indication of which would appear on the car's instrumentation when just over 4% of the charging capacity of the car has been lost.

My Sony VAIO Pro 13 actually offers the 80/20 option in Power Settings. However, I do not use it.

[Q] First charge

Hey, I just got my nexus 5 today and have been using it for a couple hours. I've always been told to dicharge new phones to about 10% and then fully charge them for 8-10 hours straight, but I'm starting to think that it only apply for old battery models. Do you think I can charge it for maybe 2 hours and then use it without damaging the battery life potential, or is it better do do full discharge/charge? Thanks.

I think you answered your own question. No need to completely charge
Sent from my Nexus 4 using Tapatalk 2

Whoever told you that was wrong, even many years ago.
These are lithium batteries, they have no memory.
I'll copy-pasta one of my very long posts on this I made a while back:
1. Charging is what reduces the life of a lithium ion/polymer battery. Batteries are usually rated between 700-1000 charge cycles while keeping 90% of their capacity.
2. Charging 0-100% counts as one cycle. Charging 80-100% 5 times counts as one cycle.
3. Leaving your phone on the charger after it is charged has the potential to reduce battery life, although this is less of a problem with newer devices as they often disconnect the charging circuit until the battery drops below ~95%. Generally only an issue if you leave it on the charger for 24+ hours.
4. Lithium batteries do not require any conditioning.
5. Most lithium devices arrive with ~40-50% battery life remaining, because this is the optimal charge level to store a lithium battery for long periods (such as sitting on a store shelf for months).
6. Slower charging maintains the battery's overall lifetime capacity better than fast charging. This is likely why the HTC One does not have Qualcomm's Quick Charge enabled. It's debateable whether you'd notice the effects over the typical lifetime of a smartphone, however (2 years).
7. Not exactly related to lithium but just in general: smartphones (and tablets, etc) have charging circuits that only draw a certain amount of amps regardless of the number of amps the charger provides. Using a 3.1 amp (tablet-level) charger is not going to significantly increase the speed at which your phone charges. Most phones only use between 0.8 - 1.2 amps. Anything over that is overkill.
8. Storing a lithium battery at 0% is really bad for its lifetime capacity. Running it to 0% generally isn't recommended all the time, but a few instances won't hurt it.
9. Recharging from 0-100 doesn't make your battery run longer. It can, however, reset Android's battery level stats so that it can more accurately state the battery level.
10. Charging from ~95% to 100% takes a long time because it must do a trickle charge. Maxing out the battery like this can reduce overall lifetime capacity, but generally not enough to matter. You'll see this impact more often in larger applications of lithium batteries (like cars).
11. Heat is the #1 killer of lithium battery capacity. The chargers are designed to regulate the heat of the battery to keep them from getting too hot for two reasons: explosions and reduced capacity. The former is obvious, but the latter isn't as much. If the battery is constantly running in a hot environment, especially when charging, it will kill the battery much faster than anything else listed here.

Alright, thank you very much.

What is a charge cycle?

A Li-ion battery has a limited numer of charge cycles, but what constitutes a charge cycle? According to some people a charge cycle is used every time the charger is connected. Another opinion is that only a charge from 0 - 100% consumes one charge cycle. So how is it really? If the first assumption is true then one should only charge when the battery is almost emty. If the other one is true then it's ok to charge at any time.

Tom200 said:
A Li-ion battery has a limited numer of charge cycles, but what constitutes a charge cycle? According to some people a charge cycle is used every time the charger is connected. Another opinion is that only a charge from 0 - 100% consumes one charge cycle. So how is it really? If the first assumption is true then one should only charge when the battery is almost emty. If the other one is true then it's ok to charge at any time.
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A charge cycle is the process of charging a rechargeable battery and discharging it as required into a load. The term is typically used to specify a battery's expected life, as the number of charge cycles affects life more than the mere passage of time. Discharging the battery fully before recharging may be called "deep discharge"; partially discharging then recharging may be called "shallow discharge.
Apple Inc. clarifies that a charge cycle means using all the battery's capacity, but not necessarily by full charge and discharge; e.g., using half the charge of a fully charged battery, charging it, and then using the same amount of charge again count as a single charge cycle. -Wikipedia
Hit thanks if I helped

Rumple007 said:
A charge cycle is the process of charging a rechargeable battery and discharging it as required into a load. The term is typically used to specify a battery's expected life, as the number of charge cycles affects life more than the mere passage of time. Discharging the battery fully before recharging may be called "deep discharge"; partially discharging then recharging may be called "shallow discharge.
Apple Inc. clarifies that a charge cycle means using all the battery's capacity, but not necessarily by full charge and discharge; e.g., using half the charge of a fully charged battery, charging it, and then using the same amount of charge again count as a single charge cycle. -Wikipedia
Hit thanks if I helped
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Ok, but that means that charging the battery a lot instead of waiting until it's almost completely drained, shortens its lifespan.

Ideally, a Lithium based battery is "healthiest" at or about mid level. A full charge cycle is technically not 0-100%, as these batteries (at least in consumer electronics) have circuitry built-in to prevent overcharging, overdischarging, and shorts. Overdischarging can cause what's called runaway discharge, where it'll keep discharging even if not connected to anything or the device is turned off. Heat, possible fire, and even explosion. Those Dell and Sony laptops that were catching fire several years ago? That was because the protection circuitry was faulty. And why you should always buy OEM factory batteries, or ones made by reputable companies like Zerolemon or Anker, and not cheap Chinese knockoffs. Hobbiests (flashlights, R/C equipment) often use unprotected batteries since they can get a bit more capacity out of them, but this is dangerous and requires monitoring and judgement.
So the answer is a charge cycle is from 0-100% and back down to 0% (or the opposite; charged, discharged, then charged - depending on your point of view), where 0% is the point where the circuitry within the battery and/or the device itself cuts the power.
There is no need to "condition" lithium rechargeable batteries (ie: fully drain them, don't use until fully charged, etc); this is a holdover from the days of nickel-cadmium (Ni-Cad) batteries, which did require conditioning for optimal performance.
The main destroyer of a lithium battery really isn't even the charge/discharging of it, but rather the heat associated with it. For example, one can keep a battery charging and charged at 95-100% while playing an intense game, downloading a large file, or running a wi-fi hotspot, but this sill quickly destroy the battery, even there's no actual "cycle" happening. The ~500 charge cycle figure assumes a typical usage of training and charging. The reason a battery is "healthiest" at mid levels is that this is where there's the least heat being generated.

Yeah, I have kind of adapted to the thought that charging whenever doesn't impact the battery in a negative way. So if my charge is 80% and I'm going out for the day, I still charge it to full 100%. If however (as the first answer suggests) this consumes an extra cycle then it would be best not to charge it. In the past this didn't matter so much but with many phones these days it's hard or even impossible for the user to replace the battery. This makes the answer to my question more important...

Tom200 said:
Yeah, I have kind of adapted to the thought that charging whenever doesn't impact the battery in a negative way. So if my charge is 80% and I'm going out for the day, I still charge it to full 100%. If however (as the first answer suggests) this consumes an extra cycle then it would be best not to charge it. In the past this didn't matter so much but with many phones these days it's hard or even impossible for the user to replace the battery. This makes the answer to my question more important...
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80-100% is not a cycle, it's 20% of a cycle. However, it is the worst part of the cycle (higher voltages, more heat). Ideally, for the battery's health and longevity over the months/years, it'd be best to keep it between, say, 30-70%. But this is impractical, potentially impossible for some, and, frankly, dangerous.
That's why I'll only buy phones with replaceable batteries. Either instantly, or without terrible difficulty when the battery hits that ~500 cycle mark. I have 3 phones: A Galaxy S4 (with a couple spares, including a 7800mAh Anker), a Nexus 4, which I've replaced the battery on, and a OnePlus One, which I know I can replace if/when I need to. I'll never get something like a S6 or Note5 or iPhone where battery replacement is nigh-impossible.

Planterz said:
80-100% is not a cycle, it's 20% of a cycle. However, it is the worst part of the cycle (higher voltages, more heat). Ideally, for the battery's health and longevity over the months/years, it'd be best to keep it between, say, 30-70%. But this is impractical, potentially impossible for some, and, frankly, dangerous.
That's why I'll only buy phones with replaceable batteries. Either instantly, or without terrible difficulty when the battery hits that ~500 cycle mark. I have 3 phones: A Galaxy S4 (with a couple spares, including a 7800mAh Anker), a Nexus 4, which I've replaced the battery on, and a OnePlus One, which I know I can replace if/when I need to. I'll never get something like a S6 or Note5 or iPhone where battery replacement is nigh-impossible.
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Yeah, it's very annoying that not batteries on all cell phones are user replaceable. And we can exchange them on some phones anyway with a little trouble, but as you write it's completely impossible with some. I put in the charge if my battery is 50% or something and I'm going out later. This should consume only half a a cycle and it's practical for me.

I now charge when the battery is like 75% before I'm going out. Is this ok or should I let the battery drain and then charge? The latter I did for a long time with a phone I had, and the battery had great performance until I sold it.