Most of us never think about the battery in our phone until it dies. When everything is working properly the battery should not be a part of the Android experience, other than not lasting long enough because we never put our phones down. The only time we ever think about the battery is when we have to charge it.
How you do that charging can make a difference, though not nearly as much as some people think. Let's have a look at the right way to take care of your battery and if it really matters.
A few facts about your phone's battery make for a great starting point. We need to know the basics before we dive into the rest.
Chemical batteries aren't safe, but there is science trying to get them there.
The battery in your phone is almost certainly a single lithium-ion (also known as Li-ion, Lion or LiB) cell. Li-ion batteries offer what's called a high energy density (power output compared to size), have almost zero memory effect and offer a moderate self-discharge rate. There are Li-ion batteries in all shapes and sizes, and while most of what we're going to talk about apply to them all we're going to focus on the one inside your phone.
The chemistry of your phone battery is usually lithium cobalt oxide-based. These types of cell offer a very high energy density but also pose some serious safety issues like the ones we saw with the Galaxy Note 7. While the actual composition can vary from manufacturer to manufacturer, generally you have two electrodes (one carbon-based and one lithium oxide-based) encased in a pressurized foil pouch filled with a lithium salt dissolved in an organic solvent as the electrolyte paste.
Charged lithium ions move from one electrode to the other through the conductive electrolyte, which is flammable. The electrolyte gets very hot when the juice is flowing and a puncture of the foil can lead to a small explosion of very flammable fluid.
The Note 7's silver lining
Some good things happened because of Samsung's Note 7 recall.
As consumers, we're more aware of the inherent danger of Li-ion batteries and Samsung is leading the charge (no pun intended!) when it comes to the science of smartphone battery safety. We'll never know exactly what happened or why, but we can be sure that every phone leaving Samsung's factories have been through a rigorous testing procedure and should be very safe. Hopefully, this can be a learning experience for all the companies who make our battery-powered things!
The companies that make Li-ion batteries are always working on ways to make them safer without lowering the amount of energy they can store. Graphene, Sulfur, and Hexafluorides are just some of the chemicals being used to try and build a better battery, and every model made is safer than the last. But lithium-ion cells are still inherently dangerous. That's why the battery in your phone is more than just a cell — it makes things a lot safer when you regulate things.
The battery inside your phone is a power cell as described above coupled with sensors and other parts like voltage regulators and an external connector. This electronic hardware monitors the electricity moving in and out of the battery as well as the capacity and temperature. They are there to shut down power instantly if they detect a short or dangerous temperature spike.
A lot of work went into making a battery for your phone that can deliver the power needed as safe as possible.
The memory effect
Battery memory effect is when the battery (not the cell itself) forgets the capacity that's not regularly charged. It's a weird concept that's difficult to fully explain.
Li-ion batteries don't have a memory effect.
If you charge your battery every time it goes down to 25% and then remove it from the charger when it reaches 75% every time, you're only charging 50% of the capacity. The 0-25% that never discharged and the 75-100% that is never charged will be forgotten. This means that over time your battery thinks 25% is 0% and 75% is 100%. You are unable to use half of the battery in this case.
As crazy as it sounds, it's true. But not for Li-ion batteries. You don't need to worry about any battery memory effect for the battery inside your phone.
From zero to 100
The battery in your phone has a "zone" that provides as much charge as possible without doing anything that affects the lifespan of the battery too much. Completely draining a battery might cause it to die and not come back.The smarts in the battery and your phone work together to make sure this doesn't happen. Overcharging a battery can cause heat that damages the cell inside it. Your phone and the battery itself work together to make sure this doesn't happen, too.
Your battery and phone are smart and make sure you can't fully discharge or overcharge things.
In a perfect world, you would keep your phone battery close to 50% charged at all times by micromanaging the time it spends on the charger to top it off when needed. This is because batteries have a useful life and it's based on charge cycles.
A charge cycle is going from dead to full (inside that safe zone described above) one time. Most phone batteries are designed to last about 400 cycles. That means if you let it run to zero then charge it to full 400 separate times the battery will no longer be able to hold a full charge and it will take more of the stored charge to normally operate your phone. Eventually, you'll notice that it takes longer to charge it and it doesn't last as long as it did when it was new.
This will happen to every battery eventually, but small "top-up" charges that don't heat things up as much have less of an impact than long charges. If you always run your battery down until it's almost dead then plug your phone in until it's full you're putting more stress on it than doing a bunch of short charges. We can't say the difference is so small it doesn't matter, but we can say that it's probably not worth the inconvenience of charging your phone five minutes at a time all day long.
Charging at night
If you plug your phone in when you go to bed and let it charge all night, it still won't overcharge the battery. But it's important to mention that you should never charge a lithium-ion battery unattended.
When the phone is fully charged the electronics in the battery tell your phone to stop sending electricity from the charger to the battery charging circuit. Power still comes in, it just doesn't work at recharging anything and goes back out to the wall socket (electricity travels in an unbroken loop to and from the power source). If your phone is still powered on the battery will discharge because it's being used. When it discharges to a certain point, charging starts again. This cycle repeats until you unplug it in the morning.
A lot of work was done to make sure the cell inside the battery doesn't overcharge at any time. Even during the night while it's on the charger. If you're going to charge your phone overnight, make sure everything works properly and you're charging properly. That means you don't have the phone under a blanket or laying on the rug while it's plugged in or have it in a thick sealed case that keeps the heat in. Plug it in (or put it on a wireless charger) somewhere that it won't get tangled up in your bedclothes or knocked to the floor.
Storing your phone or battery
Charge your battery to 50% and turn the phone off. Check it once in a while and recharge it before it drops under 10%.
Your battery will discharge in the drawer over time.
Li-ion batteries have a moderate self-discharge rate. That means when they are not being used they still will lose their charge. All batteries do this and some types (lead-acid) are bigger offenders than others (lithium-sulfur). A battery can self-discharge to zero when it's not being used even if your phone would normally shut down before you get there. Letting a Li-ion battery run down completely could cause it to not come back online, depending on the internal circuitry.
If you plan on storing a phone over the long term, drop a monthly reminder in your calendar to take it out, turn it on and charge it a little.
This means running a battery down to zero then charging it to full in one sitting. This is said to recalibrate the battery.
Recalibration won't hurt anything but it might not do anything, either.
Laptops may benefit from a recalibration cycle if the battery level icon has the wrong reading. The software that controls this on a laptop is a good bit different from your Android, though. Some experts claim you need to recalibrate your battery from time to time or when you see an issue, but others say it won;t do anything.
Fully cycling the battery in your phone every once in a while isn't going to break anything. It's not something we recommend you do every day because of that charge cycle life we talked about up the page. If you think you need to do it to fix something, go for it.
Are wireless chargers bad for my battery?
Not really, as long as you're using a quality charger of the right type.
They aren't any better than charging over a wire, either. Charging a battery makes it hot. Heat shortens battery lifespan. Once the electricity from a wireless charger passes into your phone it's handled the same way as a wired charger. Inside the battery where the chemical reaction is happening heat builds up no matter how you charge your phone battery.
Wireless charging is inefficient so it takes longer, but it also is less wear and tear on the USB socket on your phone. If you like the convenience of a wireless charger, go for it!
How about fast charging?
When using any fast charging method (Qualcomm Quick Charge, Adaptive Fast Charging, USB PD, etc.) you have a charger that is capable of supplying electricity at a higher voltage or amperage than normal. Your phone has programming on the circuit board that tells the charger how much electricity to deliver, and the charger has circuitry that listens and complies. Without both sides being able to communicate, quick-charging can't happen.
Fast charging affects battery lifespan but nobody is sure exactly how much.
There is a lot of science behind quick charging. Most of it agrees that quick charging contributes to a faster decline of the battery's lifespan. But nobody is able to measure exactly how much.
Quick charging is uber-convenient and has changed the way a lot of us use our gadgets. The best recommendation, in this case, is to use it wisely if you're concerned that it affects battery longevity. Usually, that means you need a second charger, so make sure you buy one made by a reputable company.
Using another charger
Always try to use the charger and cable that came with your phone each and every time you need to charge it. If you need a replacement or an additional charger, buy the type the manufacturer recommends. Products are designed so that the different types of quick charging products can be used on phones that don't support them (you won't get fast charging speeds) but it's still advisable to use the right quick-charge technology. If you're unsure of which kind of quick charging your phone uses, online resources like our forums are helpful, or you can contact the manufacturer.
It's also a good idea to buy new cables when you buy a new phone. Always. Charging technology change so fast that the cables you have been using for a few years might not meet the requirements and cables degrade from all the twisting and pulling they suffer through. Make sure the cables you buy match the specifications of the ones that came in the box and are made by a company you trust. Recycle your old cables and protect your expensive new phone.
Our recommended practices
- Charge your phone when it needs a charge and remove it from the charger when it's finished. Don't be afraid to use a wireless charger.
- Use quick charging sparingly if you're concerned about its effect on battery lifespan. There is little immediate damage or danger from using the right charging method for your phone.
- Try to manually shut your phone off if the charge ever drops below 10% and leave it off while charging it for a few minutes.
- Never store a phone with a dead battery and check on a stored phone periodically.
- Don't buy cheap chargers or cables from the gas station or that dude at the flea market. Use the type of charger the people who made your phone recommend.
You can make yourself crazy by worrying about the perfect way to charge your phone's battery. All the technical details about how behaviors can affect the lifespan of the battery are true, but they are also very minor in scale. Charging and discharging a battery shortens its lifespan, but a battery is useless if it's not charged so it can power something. It's OK to baby your phone's battery, but ultimately not necessary.