Technology Explained

Avoid Charging Your Phone Overnight, Here’s Why It’s Bad

Bernt Fuglseth 16-11-2018

There are many myths on how to treat your smartphone, tablet, or laptop for battery longevity. The most common ones are to regularly drain your phone to 0%, and to always charge it to 100%. You might also have heard that your battery has a memory, and that you should never partially charge the cell.


This is all completely wrong, based on older battery technology which is no longer found in most smart devices. Here’s the truth about maintaining smartphone batteries.

Charge Cycles Determine Battery Life Expectancy

charging mobile phone with empty battery symbol

You want your tech to be usable for as long as possible; warranties are invalid if you fiddle with your device. Getting the most out of your battery is increasingly important as most people are uncomfortable with changing the default battery.

Rechargeable batteries will slowly lose some capacity over time, even if you don’t use them. Through regular use of your device, you will usually notice this capacity drop after the first year. While for most of us, getting through a single day on a single charge is impossible before the two-year mark.

“Battery charge cycles” is how manufacturers specify the life expectancy of a battery. A charge cycle is defined as the battery being charged from 0% to 100% and then discharged back down to 0%. The number of expected charge cycles will tell you how many full cycles the battery can handle before it noticeably starts to lose capacity.


Lithium-Ion (Li-Ion) batteries are used in the majority of today’s rechargeable tech. You can find some form of Lithium-Ion batteries in mobile phones, vaporizers, laptops, Teslas, and even chainsaws. The most popular Li-Ion battery is the 18650. The Best 18650 Battery and How to Avoid Buying Fakes The 18650 is a type of rechargeable lithium-ion battery. Looking for the best 18650 battery? Here's what you should know about them and how to avoid dangerous fakes. Read More  This battery can take between 300 and 500 full charge cycles before being reduced to roughly 75-80% capacity, when major flaws start developing.

The King of Rechargeable Batteries: Lithium-Ion

Smartphones and tablets use a variation of the Li-Ion battery, Lithium-Ion Polymer (Li-Poly). This version of Lithium-Ion batteries is safer, smaller, and charges faster. Otherwise, the same lifespan rules apply to Li-Poly as with any Li-Ion battery.

One of the factors that increase the speed of Li-Ion battery degradation the most is charging it past 80% and letting it drop below 20%. The closer to 100% you go, the faster the chemical reaction that can create flaws will happen. If you have a Tesla, they curb the charging by default, don’t worry!

As the 300-500 number of charge cycles is based on cycles, and your battery degrades fastest below 20% and above 80%, you can extend its lifespan by avoiding extremes. Partial charges and discharges that combine to 100% are counted as a single full cycle. So if you instead partially charge and discharge your phone between 20% and 80%, research says you could get 1,000 full cycles (almost 3 years of daily charges) or more before hitting a noticeable drop in capacity.


Don’t Play Games While Your Phone Is Charging

Temperatures below 32 Fahrenheit (0 Celsius) and above 158 Fahrenheit (70 Celsius) will degrade your Li-Ion battery faster. Don’t leave your device in your car on a hot day and don’t put it in your freezer (or in the snow).

Leaving your smartphone plugged in while using it for anything intensive, like watching YouTube Google Launches YouTube Music and YouTube Premium Google has launched two new services: YouTube Premium and YouTube Music. Except they aren't really new. This is more of a rebranding exercise for YouTube Red and Google Play Music. Read More , or playing a game is a big no-no. This high-voltage and high-temperature state is the worst situation for your battery to be in.

Besides this, mini-charge-cycles can affect your battery negatively. Some parts of the battery will go through more charge cycles than others, which will age the battery. This could lead to battery cell damage, which can cause your phone to die even if your battery displays as charged.

Similarly, try to avoid the use of fast-charging technologies overnight, as this can induce a similar high-temperature situation. Fast-charging technology is not intended to be used to charge your phone from empty to full, but rather for short 20-30 minute charge periods. Li-Ion batteries will also degrade faster at 100%, so the less time your battery is fully charged, the better.


Samsung seems to be alone in that they have added a simple way to disable fast cable charging in the Samsung battery settings. This is available for both tablets and phones, so to get the longest lifespan out of your battery, you should disable this.

Use Software to Control Your Charging Habits

One way to take advantage of partial charges would be to stay close to your phone when it’s charging. However, alarms can be considered more efficient.

For Android, Accubattery displays tips to improve your battery’s health Is Your Android Battery Healthy? How to Check for Free Wondering how to check battery health on Android? Here's how to get a glimpse of your Android phone's battery health. Read More and allows you to set battery percentage alarms. Options to set up alarms for iOS seems to be lacking, but for 10$, FruitJuice has a lot of features to help extend your battery life on macOS.

Some laptops will have BIOS settings available where you can configure the maximum battery charge percentage. Lenovo has made this easier for Windows with their Lenovo Energy Management software. By installing this and selecting Optimize for Battery Lifespan, your laptop battery will stop charging at 80%.


Don’t Charge Your Phone Overnight

In general, you should try to avoid charging your phone overnight, and instead unplug your phone when you go to bed, and charge it after you wake up. During the time it takes you to shower and eat breakfast you should reach a comfortable charge percentage.

Definitely also avoid leaving your phone under your pillow while charging it. Besides the real risk of a fire, the lack of airflow can cause a high-temperature state, which will increase the battery degradation.

We’re not saying to only charge your phone in the morning. Realistically with partial charges, you will also charge it during work or in the evening. However, as much as you can, avoid going over 80%.

Although Li-Ion batteries don’t have a charge capacity memory, there is some research that says that you should fully discharge your battery at least once every 30 cycles. Your hardware can form a digital memory which will make the charge gauge inaccurate if the battery is never fully discharged. For most people this will happen naturally at least a few times a month, so we don’t recommend going out of your way to fully discharge your battery.

That said, if your phone dies randomly even though the battery gauge says you have charge left, it could be caused by miscalibration (or a faulty battery). If calibrating your battery (here’s how to do that on a MacBook Calibrate & Maintain Your MacBook Battery For Best Performance If you correctly calibrate and maintain your MacBook battery, it's possible to improve performance and put off replacing it for as long as possible. Read More ) doesn’t fix the issue, then faulty batteries should be a valid claim if your battery is still under warranty.

Reduce the Battery Drain on Your Device

Samsung power saving mode

Beyond watching the temperature and charge percentage of your device, you can further extend the battery life by reducing how often you need to charge it. Fewer charges mean fewer cycles, which means a longer life for your battery and your device.

Reducing the screen timeout duration and turning down the brightness settings will have the biggest impact. There is a reason why tests use Screen-on-Time (SoT) when testing for battery life on smartphones. Apple has introduced some useful   features that use SoT to help curb your phone addiction in iOS 12. iOS 12's Screen Time Feature Will Curb Your Phone Addiction Do you use your iPhone too much? The new Screen Time feature in iOS 12 can help you cut back on your phone addiction. Read More

In addition, most smartphones and some laptop operating systems will have a form of battery saver option. Turn this on when possible. There are simple steps to configure your Windows 10 device to optimize your battery life How to Optimize Windows 10 for Battery Life Battery life is a pretty important factor for mobile devices. While Windows 10 does offer new features to manage power settings, the defaults are not necessarily contributing to optimal battery life. Time to change that. Read More  without extra software.

Battery saver will rarely affect your experience of the device negatively, especially when you are not actively using the device.

Disabling signals like Bluetooth, GPS, Wi-Fi, and mobile internet are common tips to save battery life. These days Bluetooth and Wi-Fi signals are pretty battery efficient. Disabling GPS and the mobile internet signal can reduce the battery drain noticeably on most devices.

Tips for Extending the Lifespan of Your Battery

In the short to medium term, you may not notice much difference. However, you’ll be happy when your phone still survives a day on a single charge after a year. Following these tips, your battery should not hit 80% charge capacity until after 2+ years of use.

  1. Use partial charges to keep your battery between 20% and 80%. You can use software to notify you when your battery reaches 80% so you can unplug it.
  2. Reduce the amount of time your battery is kept at 100% charge by not charging your phone at night. This is when the battery will degrade the fastest.
  3. Avoid using fast-charge for longer periods.
  4. Keep your device at room temperature, and avoid extreme temperatures.
  5. Where possible, set the maximum charge of your battery to 80%.
  6. Reduce the battery drain of your device by turning off unnecessary services. Use battery saver to get even longer use from every charge.
  7. If you are storing batteries unused for longer periods, discharge them to 70% and store them somewhere cool. Storing batteries at full charge will cause them to deteriorate faster.

If all that isn’t enough, the pressure to keep upgrading our devices has a real impact on the environment. In fact, as of 2016, we only recycle about 12.5% of our annual electronic waste. The Truth About e-Waste Recycling and Its Effectiveness The world is producing more e-waste than ever before. We should be recycling it, but there are some problems there that you may not be aware of. Read More  By getting longer use from your tech, you can pat yourself on the back for helping save the planet.

Related topics: Android, Battery Life, Debunking Myths, iOS.

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  1. Hatty
    November 21, 2018 at 2:46 pm

    Don't overnight only applies to Samsung phones because they don't care about properly testing their products. Every Samsung product catches on fire due to improper testing and/or their products rarely last beyond two years.

    Samsung steals most of their technology from other companies and then attempts to beat the company they stole from to the market.

  2. Ron Miller
    November 19, 2018 at 7:46 pm

    Man, there are a lot of negative replies in this thread . . . and not a little hedonism. What the author writes here is very true of Li-ion batteries, though. If you don't mind the waste and expense of replacing batteries annually, disregard the article, but that's no reason to accuse the author of spreading "BS." In my Tesla, I have no choice but to follow this advice because it flat out works and because replacement of the battery pack is not a reasonable option economically. In my watch and cellular phone, I avoid fast charging altogether, and, as much as possible I try to avoid charging past 90% and discharging past 30%. It's easy, not an imposition, as long as one owns more than one charger.
    To each his own, but this article provides sound advice

  3. JK
    November 19, 2018 at 5:08 pm

    I appreciate the tip on long-term storage, since I use my phone only for travel--the other 49 weeks a year it sits in a drawer. I still do not see the need for one in daily life. Once upon a time humans walked the streets with autonomy; now everyone's plugged into these things like damn umbilical cords. There's nothing that comes through a phone that can't wait until I get home.

  4. Waldo Kemper
    November 19, 2018 at 1:51 pm

    Aside from the warning to NOT charge the phone under my pillow, the rest of the article is useless. My car would last a lot longer if I didn't drive it. If I took my kids phone away from him because it's charging, he'd lose usage 90% of the time.
    My goal of having a phone is 100% utility. If I have to change the batteries once a year, so be it.

  5. anonymous
    November 19, 2018 at 12:34 pm

    I'm glad the the comments are sensible enough to call out on the Author's bullshit.

    Even if for the sake of argument that it isn't good for your battery, I'd rather have a battery replacement every year than to go through this kind of bullshit with a mobile device because I have a life. The way you do this kind of defeats the purpose of a smartphone in the first place.

  6. Brett Rieck
    November 19, 2018 at 4:53 am

    I have an iPhone 4s that I haven't allowed to upgrade. It is plugged in 100% of everyday and there isn't a single issue with the phone. My phone has no issues whatsoever. What does that say about the OS?

    • Voice Of Reason
      November 19, 2018 at 12:04 pm

      What does it say about you?

    • michael
      November 19, 2018 at 5:22 pm

      Why you would use a phone plugged in 100% of the day... aren't they supposed to be portable? Sounds like a desktop computer to me. If it's plugged in all day, why are you bothering commenting on a article about batteries? Your battery is a paperweight, nothing more (and manufactured by Samsung, not Apple, so I wouldn't be too quick to praise the almighty Apple gods too quick)

  7. Questions
    November 19, 2018 at 3:55 am

    Not a techie, but I have plugged in my phone (2nd Gen Motorola MotoG) overnight for about 4 years now and it's still hanging in there with no problems. Same with my commuter electric-assist bike; battery lasted eight years, including being plugged in all winter because I don't like riding in the cold and dark. So perhaps batteries are a little hardier than the author thinks.

  8. TheJamin
    November 19, 2018 at 3:49 am

    Obviously whatever putz wrote this article has never depended on his phone for daily business. Try waking up and starting the day with only a 70-80% charge and see how far you get...oh, and don't forget we can't charge while running battery draining apps either! My phone would be freaking dead or unusable by noon each day.

  9. tyrdofrecyclednooz
    November 19, 2018 at 3:40 am

    Did it have to take 20 paragraphs to inform us of the do's and don'ts of battery charging?
    Next month I'll be another article somewhere stating the exact opposite of what to do and what not to do.
    Remember when they said eggs had so much cholesterol and then years later, another group of experts announce that eggs don't have as much cholesterol as they thought? And drinking coffee was good for your heart and then some medical experts come out and say that the caffeine will kill us then 5 years later they're telling us to drink up because of the health benefits of antioxidants Etc. Just cut the crap and let us figure it out for ourselves !

  10. Tara
    November 19, 2018 at 3:39 am

    It states to not charge overnight. However, my children are to go to school with fully charged ipads, and it isn't possible to charge in the morning, before leaving, and they are not supposed to charge at school. (Can you imagine say 1000 students needing to charge an ipad all at once?) While I don't always plug my phone in overnight, I sometimes do. While I can technically charge my phone at work, it is highly discouraged because we are not supposed to have our phones on us while working.

  11. Brian
    November 19, 2018 at 3:34 am

    One of the more accurate articles I've seen on cell battery charging. One other thing I would add is that Apple and assumedly all other phone manufactures have battery engineering teams dedicated to fine tuning how the phone charges itself. The phone uses data to determine when to charge at full blast and when to trickle charge the phone. For instance they are most assuredly trickle charging the phone when it gets near 100% charge as it would prematurely wear out the battery and generate lots of heat if you hit it with full force. So in addition: 8. Don't think you can outsmart your phone's charging software.

    • Tim Ho
      November 20, 2018 at 12:29 am

      Great Observation / comment. Competition would practically mandate manufacturers to include such circuitry. Thanks

  12. Disappointed
    November 19, 2018 at 3:30 am

    You did not explain why you shouldn't charge your phone over night. You made the point but provided no evidence, and that's what the article is named after! It's the reason I clicked it! The only thing that links to that is the phone under the pillow issue, which is a really specific situation. You don't even provide a link to the part that says "some research".

    Y'all made an article about disproving myths but failed to cite anything, meaning you're just spreading more myths.

    • Emily
      November 19, 2018 at 4:25 am

      Because there was one line of phones that had exploding battering in the news a few years ago, no one should ever let it out of their sight again.

      • Doc
        November 19, 2018 at 11:24 pm

        The Samsung Galaxy Note 7 had "exploding battering" (snicker). Aside from electric scooters ("hoverboards"), there have been few widespread reports of bad or dangerous batteries.

  13. PHX
    November 19, 2018 at 3:25 am

    Literally the most unrealistic advice about phone charging ever. Who tf keeps their charges only between 20% -80% except perhaps the most anal technocrati. Modernity has us having to juggle a million banal and mundane things everyday, being watchful that my phone charge doesn't go over 80% or making sure it doesn't stay 100% charge for more than 10 mins is going to be at the bottom of a very very long list.

    • Emily
      November 19, 2018 at 4:23 am

      That's because the author's an idiot who doesn't realize that "100%" is actually somewhere between 80 and 90%, and "0%" is actually around 10-20%. Or maybe we can assume that the engineers who've been developing charge controllers for these things for two decades have no idea what they're doing, so we should worry about results by grad students who use actual hard 0-100% cutoffs to destroy batteries.

      With diligent work, you can probably find a way to discharge a cell phone battery all the way to 0, but it'd be essentially impossible to get it to 100% of its objectively rated capacity short of bypassing the controller and forcing energy into the cells direct.

  14. S
    November 19, 2018 at 2:57 am

    Running a nexus 6 bought new in 2014 its 4 years old. I have always charged it overnight. Only thing is last year and this year it may shut down under 50% if it gets below freezing and using power hungry applications. Mind you this is normal with any battery. Its good to factory reset and re flash the system once in a while aswell to keep the phone running optimum. There are different variations of lithium batteries tho ranging from 4.1 volts top charge to 4.3 volts. 4.1 will have a longer life but not put out as long. Where as 4.3 will have a shorter life but put out much more power. usual is 4.2 volts. But its all hardware controlled set by the manufacture and the battery will automatically disconnect from the power source once fully charged as to not over charge. Hence why you should use the suplied AC adapter. If you do the math the charge cycle is usualy from somewhere arround 3.4 volts to 4.2 on average 3.4-4.2 is 0.8 volt range. If you charge 80% of 0.8 that leaves you at 4.04 volts and never obtaining a full charge cycle. Always use manufacture recomendations. Their the ones that built and engineered the device, they will know whats best for their product. Personally i like the discharge as much as possable preferably till the battery saver comes or it dies then give it a good full charge.

  15. Alan Cooper
    November 19, 2018 at 2:55 am

    I've been told (see website article on battery charging) that
    "Deep discharge damage. Draining down rechargeable batteries too deeply can cause immediate and permanent loss of capacity. Up to 40% each time deep discharge occurs."
    This is opposite of what you say. Who is correct?

  16. Not My Atari
    November 19, 2018 at 2:45 am

    Is this article crap? It sure reads like crap. Seriously, "don't plug in your phone at bedtime" with a bunch photos of burned up Samsung phones? Please.

  17. k.t
    November 19, 2018 at 2:02 am

    premium bullshit

    • peanut gallery
      November 19, 2018 at 2:11 am

      yep, mostly nonsense. and even if wasn't why would it be worth anyone's time to tiptoe around using their favorite device like this?

  18. justaguy
    November 19, 2018 at 1:37 am

    The article started off well, except the title. Then it recommended some "battery health" apps which do absolutely nothing.

    WiFi is less power-hungry today, but it should still be turned off when not using it. It also keeps the marketing apps from tracking you at traffic lights and inside shops. Same for bluetooth.

    The advice to avoid using fast-charge and not keep the device under a pillow are all good. However not charging during the night is a bit silly, I'll explain why.

    Most of the premium manufacturers today use power-management chips that can preserve battery life. So leaving something plugged in does not mean it will charge. Instead, the phone will use the electricity from the cable and leave the battery to slowly discharge itself. This is a bit bad, for more complicated reasons, but the phone will still report 100% even though it's draining towards 95%. The MacBooks have been doing this since almost 10 years ago.

    The quoted life of 300-500 is typical, but premium manufacturers build in battery systems that can reach well over 1000 and often 2000.

    The best advice is to enable a charge threshold (like Lenovo has) if available. 85% should provide 3x the battery cycles than usual.

    The conclusion might be that you get what you paid for. I have Apple stuff that has gone >1000 cycles and still maintains >50% of the charge. I had cheap phones that used to die at 50% battery after 150 cycles. And have many others in-between, just for anecdotal evidence: Lenovo ~700 cycles, Samsung ~800, Kindle ~700, Motorola ~800, HTC ~500, ...