[Guide] The Care and Feeding of Lithium Polymer Batteries

Rukbat

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[Updated 2/29/20]

You've had your phone for 7 months, but the battery isn't holding up all day, the way it did when it was new. It's out of charge by 2 or 3 in the afternoon now. What's going on? Is this the bad battery life you've heard about this phone? Or was it the update you got 2 months ago?

Neither one, actually. If you're like most people, you had the phone set up in the store, took it home and started using it. When it told you to charge the battery, you plugged the charger in. When it was fully charged you used it, waiting to charge it again until you got the message to charge it again.

In most phones, that message comes at around 5%-10% of charge. Discharging a lithium battery that far will give you a lifetime of about 300-500 charges, but the battery will start losing capacity long before that. So after 150 charges you're noticing that loss of time until it has to be charged again. Maybe not much, but it used to last until you got home from work, now it's crying for its charger before you leave work. Maybe 5% loss of capacity, but a forecast of things to come. By the end of a year, you believe the stories that this phone damages batteries.

The battery may have been sitting on a shelf at the battery manufacturer's plant for a few months after it was made, starting at about 40% charge. By the time it got to the phone manufacturer it was down to 35%, so they put the battery into a charger, brought it up to 45%, checked the phone to make sure it worked with that battery, turned it off and packed it up. Then it sat for another few months before you bought it. So far, so good. 40% is the right charge level for long term storage - both manufacturers know that - so the battery should be fine. (Lithium batteries discharge just a bit just because of the chemical makeup of the battery - it's caused self-discharge. [Most battery chemistries have that "problem", which is why the AAA batteries you buy in the store have expiration dates.] Just sitting on a shelf. The more charge in the battery, the faster the discharge. But if the charge gets too low, there are chemical changes taking place that shorten the life of the battery. 40% is about the best point. Low enough so the self-discharge is pretty slow, high enough to not shorten the battery life much.)

Now you get the battery and start using it. Charge the battery to about 98% to 99% - then unplug it or take it off the charging pad. Charging past 100% is unhealthy for the battery - and if you're not watching it, and the charging chip fails, the charger could keep charging the battery after it reaches 100%. The more we work on batteries, the more we learn about them.

Now you use the phone until it tells you to charge the battery, right? Wrong. Try to never let the battery get below 40% charge. Letting it get below 50% is where the lifespan starts dropping. 45% won't shorten the life enough to matter, but 40% is the absolute limit. 20%? Half the life. 5%? The battery probably won't last a year. And I'm still using the batteries (always 2 - if the one in the phone drops to 40% and I have to have the phone running a few more hours before charging, I swap batteries - we can't do that any more in most phones) in my Motorola V551 that I had when I opened the box in 2004. I'm still getting about 95% capacity. And, aside from long-term storage, they've never dropped below 40%. The phone is pretty useless - it has a 640 X 480 camera and it has a contact list. And it can access the web and do email. It was a very innovative phone in 2004. Why do I still use it? If I'm going to be in a place where someone might "find" it (people don't actually steal, they just find things - in your pocket), or where it may get damaged, it's a lot cheaper buying a V551 (or equivalent) on Craig's List for $20 (and that's a ripoff - my Samsung Precedent - an Android phone running Gingerbread - isn't worth more than that) than replacing a "found" Note 3. If I'll be in an area where the phone could get damaged, could get wet (but see Oh, no! My Phone got Wet!), and I still want to have a phone with me (I'm 77, you never know), I'll take the V551 with me. But I check the batteries every few months, and keep them around 40%. They're over 10 years old, and still ticking.

(Conditioning:

With modern lithium batteries, we no longer have to condition them.)

**Temperature

You're out in the cold. It's winter in central Alaska (people in Miami consider 80° "cold"?) and the temperature outside is minus some double digit number. You're fine. Two pairs of wool socks, insulated boots, thermals, a 100% down parka. But your phone is in an outside pocket. (You're not going to unzip your parka in this weather to get your phone.) The gel electrolyte in the battery is close to becoming a hard solid. The phone rings. You answer it. The battery, which was fully charged when you left your house, goes dead in 5 minutes. Huh?

Batteries are much like people when it comes to temperature. They function best at about room temperature. By freezing (32°F, 0°C), they've lost about half their capacity. It's linear - if the battery still worked at about -10°F (lithium batteries stop working at about -4°F), it would have no capacity at all. It's temporary - warm the battery up (assuming the gel in it didn't freeze into crystals that damaged the battery) and it's still good. But using the battery when it's cold - even just having the phone turned on - can lower the capacity dramatically.

High temperatures are also bad. If the phone shows a high temperature warning, turn the phone off. If the battery comes out, take it out until it cools off. (It's possible for a lithium battery to go into thermal runaway - it gets hot faster than it can radiate the heat away, making it get hotter, making the situation worse, etc., until ... If you're lucky, the battery covering bursts into flame and you've lost $15. If not, and the pressure inside the battery builds enough, the battery explodes. The two places you don't want that happening are in your pocket and upwind of you. (Why upwind? A burning lithium battery produces very irritating, not to mention poisonous, smoke, and you don't want to breathe it.) Battery damage to the phone normally isn't covered by the warranty. (Sony had to eat a lot of batteries due to a defective batch, about a decade ago, and all their Note 7s in 2016.)

Oh, on the subject of danger, please don't throw a dead lithium battery in the trash. Aside from there still being enough power in it to start a fire if it gets shorted in there, it's poisonous. There are many places that accept batteries for disposal. We throw out enough junk every day. Dropping a battery in a store's battery disposal bin isn't that difficult. (If the battery isn't removable, you're probably going to have it replaced by a repair shop if it needs replacing, so don't worry about it - they know how to dispose of batteries.)

Just to put two myths to rest here.

Myth 1 - "Calibration"

You'll see that doing a single conditioning cycle (draining the battery very deeply) will "calibrate" the State of Charge indication - the SoC - (the 75% or whatever number you see as the current state of the battery). It won't. It has nothing to do with that. Calibration affects a file - the one that keeps track of which app is using what percentage of the current being drawn from the battery. After 10 charges or so, that file is pretty well calibrated. You don't have to do anything to make it as accurate as it's going to get. You're just wasting battery longevity. (And draining the battery deeply shortens its life - even if you only do it a few times.)

The indication doesn't seem to be right? That's because it's an approximation. The actual SoC can only be determined by analyzing the chemicals in the battery. The battery stores chemical energy, so its SoC is actually its "which chemicals are present in what percentages" state. Measuring the voltage across the terminals of the battery with a load on it (which is what you're seeing with the "state of charge percent") is the best we can do, so that's what we get. If it's off, that's because your battery isn't following the standard voltage vs. charge curve, and that's due to the chemicals in the battery. You can't "correct it". If it's that important to you, get the battery replaced. (It's not important - if you recharge at 45% or thereabout, the battery will have a long life. If it's actually 44% or 46%, it doesn't matter. [If it's bad enough that the battery is at 10% charge when it's indicating 45%, the battery is at end of life, so you need a new one anyway.])

If you really want to calibrate the reading the phone has to be rooted, because a system file has to be modified to contain the voltage that's "100%" for that battery in that condition. Use Battery Calibration and follow the instructions contained in the app. (Deep discharging the phone doesn't recalibrate anything although, in some phones it resets the % used graphs, so it appears to have done something to the battery.)


Myth 2 - Charging a battery from 0 to 100% in minutes (or other "fast charge" nonsense)

Lithium batteries can be charged at a 1C rate - IOW, the capacity of the battery. So if you have a 3200mAh battery, it can be charged at 3200mA (or 3.2 Amps). The charge from 0 (which you should never do to a lithium battery) to 100% will take an hour plus inefficiency (turning electrical energy into chemical energy - charging - is very inefficient, as is any energy conversion), which means about 90 minutes. The recommended charge is 0.75C, or 3/4 of the battery's capacity. So for the above 3200mAh battery, a "fast charge" would be 2400ma (2.4 Amps). Most phones are designed to charge at around 0.5C. Charging from 45% or 50% to 100% at 0.5C is a little faster than a 1C charge from 0% to 100%, so about 80-90 minutes.

You CAN NOT make the battery charge faster by using a larger charger. Electricity isn't pushed by the design (or capacity) of the charger, it's drawn by the design of the load (phone, powerbank, etc.) If the phone is designed to draw 1200mA (1.2 Amps), that's what it will draw, as long as the charger can supply that much. Connect it to a 100 Amp charger and it'll still draw 1200mA. (Your house, if you're in North America, is a 200 Amp [or larger] "charger". A 100 Watt light bulb still draws just under 1 Amp.) The only way to get the phone to draw more current is to raise the voltage coming from the charger - and if you're lucky, all that will do is damage the phone to the point that you'll need a new motherboard. If you're not lucky you'll be able to toast marshmallows in the resulting fire.

(Fast charge phones just change the parameters inside the phone to draw more current [by raising the voltage fed to the charging circuit in the phone], so instead of a 0.5C charge, they're doing a 1C charge - usually from 0% to about 70%, but if you're treating the battery right, that's only from 50% to 70%, so you're not saving that much time. I don't know about you, but I wouldn't let that be a consideration when I'm looking to buy a phone. And I'm 77 - I probably have fewer minutes left than you do. Even giving you a 1C charge from start to 100% won't cut the battery's life by more than a tiny faction of a percent, if that, but it will cut the charging time considerably. But charging at more than 1C is considered a destructive test, not a charge - you do that to see how long it takes the battery to fail at various charge rates - and it's usually a very short time.)

Oh - one more myth - that apps that save battery actually save battery. There are very few apps that actually save any battery power - Greenify is one of them. Apps that "clean RAM" or "optimize" the phone use more power than they save. (I've ran [during December, 2019] some tests on a few of the more popular ones, and didn't find one that not only didn't save power, but cost power - the charge lasted a shorter time running the app than after it was uninstalled.] Any developer who writes an app that "cleans RAM" is a developer telling me that he thinks that Android runs the way Windows does - when, in fact, it runs just the opposite way. Windows likes as much free RAM as possible. Android wants as little free RAM as possible. (One of the Android developers explains why at Multitasking the Android Way if you're interested.) If you want to get on my list of "I won't bother to read the blurb on your app's Play Store page" list, write an app that cleans RAM. If you don't know Android well enough to know how wasteful that app is (in both speed and battery), I don't trust anything you write for Android*. You have to know the environment you're writing for. (I've been earning my living designing code for over 45 years, but I have yet to write my first serious Android app - and probably never will. I don't even know the API for writing to the screen in Android. Turn me loose on a Windows machine and it'll wash your dishes and mop your floors. But you can't write an app for an environment you don't understand, and "clean RAM" says, to me, "I don't understand Android as well as someone who won't even attempt to write an Android app".)

More "myths" I've seen posted on Android Central:

There's no such thing as a new 3.8 Volt lithium battery, it's the same old nominal 3.75 Volt battery with a new label. If that makes you feel like the battery is worth more than some other manufacturer's battery, it did its job. But a volt meter will show that a fully charged 3.75 Volt lithium battery and a fully charged 3.8 Volt lithium battery have the same open-circuit terminal voltage. (There are lithium batteries that produce more voltage - but they're not used for cellphones.)

You don't use a charger rated at "at least 4.35 Volts" - that's the voltage applied to the battery terminals by the phone when it's charging the battery. Phone chargers are nominally 5 Volts (which means that some of them are rated at 5.2 Volts - and the phone really doesn't care). Make sure that the charger is capable of at least 1 Amp (or 1,000mA - same thing, like 100 pennies or one dollar). The old 500mA and 750mA chargers will take longer to charge the phone - current phones are designed to charge from the wall charger at a higher rate than that. (Most chargers are rated at least 2 Amps [at 5 Volts - different currents at 9 Volts, 12 Volts, etc.] these days. The difference costs the manufacturer less than the label on the charger, since most chargers are a couple of cheap parts in a plastic case - the cable and plug are a large part of the cost.)

Live long and prosp... er, keep working.

It's been discovered that one of the worst "ram cleaning" apps gobbles up all your data - phone numbers, email addresses, etc., and sends them to its home server. If for no other reason, that's the reason you shouldn't run "ram cleaner" apps. (I'm not naming it - since they're all useless at best, stay away from all of them.)
 
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Rukbat

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It's all palgiarized - from me. After 72 years with only one mouth and 2 ears, more came in than went out. (No doctorate, though, not even a Master's - I hated school.)
 

UpTheDumper

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So... New phone drop to "charge" level, charge to 100% plus 1/2 hr. Do this three times, and then never let it get below 40%? Why doesn't someone make an app that doesn't let you go below 40%? Like 40% with this said app is the new "dead".. better yet, why the hell doesn't the manufacture do this in the first place so it's impossible for someone to ruin a lithium battery?

Posted via the Android Central App
 

Aquila

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So... New phone drop to "charge" level, charge to 100% plus 1/2 hr. Do this three times, and then never let it get below 40%? Why doesn't someone make an app that doesn't let you go below 40%? Like 40% with this said app is the new "dead".. better yet, why the hell doesn't the manufacture do this in the first place so it's impossible for someone to ruin a lithium battery?

Posted via the Android Central App
Most will still advocate against conditioning; fast charge and discharge both lead to high temperatures and more than necessary wear. That said, three out of hundreds of cycled is negligible to most.
 

B. Diddy

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It's not that you can never let it drop below 40%--it's more that you should make it a habit to start charging at around 30-40%. The more often you let it drop to single digits, the shorter your overall battery lifespan will be. Since you have an S5 Active, you have a big advantage over lots of other people because you can replace your battery easily. So it's not as important for you or other owners of phones with replaceable batteries.
 

RG57

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When I have to start charging?

Hello,
Thank you for your excellent work, I have learned a lot. But I need one more piece of information: I will buy a new phone (exactly a samsung note 4) which will come with a battery full at a certain level, say 50% or 30%. To condition that battery, do I need to use the phone first until it drains the battery to 0%, or start right away charging until 100% + 30 mn. what ever it's remaining charge?
Thank you in advance for your prompt reply,
Regards,
Raif
 

Rukbat

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Re: When I have to start charging?

Charge to 100% + 30 minutes (the moment the phone says 100% it's about 98% charged) first. Then use until the phone shuts off. Three cycles.

Using it the first time probably won't hurt, because most phones these days come fully charged, but charging first can't hurt, and it probably won't take much time. (If you plug the charger in, turn the phone on and it says 100%, it came fully charged and you can skip the first charge.)
 

Chitown28

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Re: When I have to start charging?

I always set my phones up myself and charged them before i turned them on. I will take it out the box when i get home plug it up and let it charge for about 4hrs then i use it till it gets down about 10-15% and then charge it up again and keep repeating this cycle for a few weeks is this ok?
 

Rukbat

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Let it charge until the phone tells you to unplug it - then add another half hour. (The only way we have of measuring state of charge is a bit inaccurate - it says the battery is fully charged at about 98%.) Let it run normally until the phone tells you to recharge it. Repeat the cycle twice more - a total of 3 charges and 3 discharges. Then try to not drop it below 40%.
 

Karl K

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Thanks for the info! Finally found credible information on battery life. I still have a few questions though. I'm in conditioning now, using my phone until 5% and fully charging it. About the part of keeping over 40%, is it okay to charge often to do that, like when you're on 70%?
 

roshart

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I have had my Samsung Galaxy S6 for three weeks now and have only just discovered that the battery should have been "conditioned" from the outset. Is it worth going through the process now, having just done the initial charge plus 30mins at the start. I haven't let it run down three times - has the level already been set now? I am amazed that no-one tells you this when you buy a relatively expensive piece of equipment for which you cannot replace the battery yourself!! Thanks in anticipation.
 

rockshj

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i have moto g3 from past three weeks.. how should i charge my phone.. for bttr battry lyf... nw a days m getting 6-7.5 hrs SOT
 

atzau

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I have had my Samsung Galaxy S6 for three weeks now and have only just discovered that the battery should have been "conditioned" from the outset. Is it worth going through the process now, having just done the initial charge plus 30mins at the start. I haven't let it run down three times - has the level already been set now? I am amazed that no-one tells you this when you buy a relatively expensive piece of equipment for which you cannot replace the battery yourself!! Thanks in anticipation.
^^^ I'm in this situation as well... looking forward to finding out the answer.
 

FatiimaAch

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So i should start charging at around 30-40% and let it fully charge to 100%, is that safe for the battery ? I have the samsung Note 5.please answer me
 

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