The reality of leaving your phone plugged in overnight

A big part of our interconnected, tech-heavy lives is the maintenance of our devices. We back up hard drives, we install updates, and we keep batteries charged. In the case of your phone, charging might coincide with the time that your own head hits the pillow for a mental recharge. You can plug your phone in, set it next to you, and not have to worry about it until morning. But is the battery being damaged while you sleep?

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What happens when I leave my phone plugged in overnight?

What happens when I leave my phone plugged in overnight?

For the most part, leaving your modern phone plugged into a charger overnight isn't going to be a problem. Inside is most likely a lithium-ion battery, which is partly responsible for how thin phones have become, as well as how they can last through a day with life to spare. They also don't come with some of the same problems as older nickel batteries used to have, like losing track of the maximum charge threshold.

Lithium-ion phone batteries are not made to last forever. As soon as you deplete it and charge it — known as a cycle — you've begun a process that will eventually lead to your phone either needing a replacement battery or you in need of an entirely new phone. Battery University, in an article about how to prolong the life of lithium-based batteries, claims that on average you can get about 400 cycles out of a device.

Though it usually only takes a couple of hours to get a full charge, let's say your phone is plugged in for about seven or eight hours while you sleep. Once the battery hits 100 percent, it's going to stop charging thanks to software there to determine when it's had enough. Unless there's a breakdown in the process, you shouldn't expect to see a ballooned battery poking out of the back of your device.

Heat will harm your phone's battery

Your phone is smart enough to not take damage by overcharging, but there's still an issue. Charging a phone causes heat, which — along with cold — can damage a lithium battery. Prolonged periods of elevated heat will degrade a battery faster, as can be seen in this chart from Battery University.

Temperature charging chart from Battery University

Temperature chart courtesy of Battery University.

Regular charging shouldn't cause a phone to reach a harmful temperature, but if you like to keep your phone next to you in bed while it's plugged in, the blankets or pillows probably aren't doing it any favors. If possible, leave the charging phone next to the bed where it has room to breathe. A bulky case will also no doubt contribute to unwanted heat, so consider removing it as well.

What can I do to prolong the life of my phone's battery?

I miss you, Lumia 950 XL

Batteries are in a constant state of degradation, and you can expect to get about 400 charge cycles before you notice a serious hit to performance. In another chart from Battery University, we can see that lowering the maximum charge can give a battery more cycles, but will ultimately lower its maximum threshold for stored energy.

Voltage chart courtesy of Battery University.

If you keep your phone's battery somewhere between a 40 and 80 percent charge, you should be able to get more life out of it in the long run. This doesn't exactly work for those who like to charge overnight, but it's certainly an option for those who get in a quick charge here and there over the course of a day.

Those who are frustrated with a device that gets to 30 percent battery and powers down can try a calibration to get a more accurate reading. Let your battery drain completely and recharge to 100 percent while it's powered down. Once you turn it back on, the gauge should give a more accurate read of the time you have left before you'll be looking for an outlet.

How to recalibrate the battery in your Windows 10 laptop

More resources

If you're wondering how all of this applies to the battery in your laptop, be sure to check out this other guide with similar information!

The reality of leaving your laptop plugged in

Cale Hunt
Senior Editor, Laptop Reviews

Cale Hunt is formerly a Senior Editor at Windows Central. He focuses mainly on laptop reviews, news, and accessory coverage. He's been reviewing laptops and accessories full-time since 2016, with hundreds of reviews published for Windows Central. He is an avid PC gamer and multi-platform user, and spends most of his time either tinkering with or writing about tech.

  • "Let your battery drain completely and recharge to 100 percent while it's powered down. " Not possible with that 950XL shown there.  Microsoft phones always power on when there's enough juice.  
  • Personally I don't charge my phone over night, I worked at Verizon for 4 years and most of our demo units would balloon in under a year, some bad enough the phones began splitting in half or had screens pushed out of place. It's also my understanding that a battery can actually become damaged if left near depleted or near a full charge for lengthy amounts of time. It's the reason the vast majority of our phones came new with a 40 to 60% charge.
  • Demo units usually play promotional looping videos on them indefinitely, producing heat along (most of demo phone I handed on were all warmer than my body temperature), so perhaps it's what caused the battery cycle to quickly depleted and got inflated in no time.
  • Even when your phone reports 100% charge it isn't. It's probably more like 85% of actual capacity. Same with discharge, it never reached 0. That's the job of the BMS, so you don't have to worry about it. 
  • What is this infatuation with android phones here on Windows Central? Smh
  • Unfortunately Microsoft seems to be treating Android as the new Microsoft Mobile now that they've officially killed Windows 10 Mobile. Hopefully this will start to change with the Andromeda device.
  • Windows Phone for all intents and purposes doesn't exist. Microsoft is throwing their half assed support behind Android for now. We'll see what happens in the future, but don't hold your breath.
  • I have a 950xl, had it since new oct/nov 2015, almost 2.5 years. Plugged it in every night in that period - 800 or so charge cycles. It's still as new. Clearly things aren't as b&w as suggested.
  • Mine is always plugged in overnight too and is just as old. Wear level still at 0% at least according to Aida64. Edit: Should also add that its also plugged in for most of the day at work too.
  • Aida64's battery wear report can't be trusted. It shows for my 950L's also 0% wear, although it's the original battery, and i read about cases where people changed batteries showing 0% wear on crashing phones and thereby fixing their problem. There is no way a battery after years and several hundred cycles has 0% wear, there is just something wrong with Aida and it's a pity as i would very much like to know the state my battery is in.
  • I do not use any app to so the state on my battery.  I know by daily use how my battery is.  My 950 is old, my daily driver and still easily last thru the day.  I only charge overnight.  I rarely have to any other time and if I do, it is for a short time driving home. I am sure after two and a half years there is some degrading but I have not noticed it.  The quality of the materials in the battery would have to be taken into account as well as how hard you use it.  Quick drains and all.  
  • One positive of buying Nadella products; they'll be abandoned before the battery dies. :)
  • I've had my L730 for 3 1/2 years and could charge it two time a day many time and the battery still works good enough that I don't see a need for a new one.
  • My 950xl is on my wireless charger every night. Love the facility. However, the battery has seen better days. Soon depletes with even light use, Edge is a devil of an app. Got to be honest though, it was only around Tue 2yrbanniversarybthat I noticed how bad it had got.
  • Moving from my Lumia 950 XL to Android, I got me a Sony Xperia XZ Premium which I quite like. The Sony software has a battery care mode. It starts to recognise when I ordinarily charge my phone and when I take it off the charger. The software limits the charging through the night and will then allow a charge to the reach 100% before I take it off the charger. It will warn me if I've take the phone off the charger before it's reached the 100% mark.
  • I went from 950 to XZ Premium as well. I am consistently impressed with its battery life (on light days at the office I return home in the low 90s), and love the battery care function.
  • My Nexus 4 was plugged in over night for over 5 years and it was only in the last six to 8 months  of use that the battery started to lose  charge quickly.  At the end of the day, some people may have a problem, others don't, it is just the luck of the draw.  
  • I always plugged in my Moto X overnight. 4 years later and the battery never degradeed. It still works like new. I got the OnePlus 5T now though. Its even better than my Moto X. 2 days without having to charge. When I do charge, its with dash charge. It only takes 60 mintues to go 100%.
  • I have always left my phone to charge overnight and never had a battery fail in less than two years, other than a battery that was weak from the manufactured date. Batteries now (along with chargers and software) have gotten much bwtter over the last 5 years. Hopefully this will be a non-issue in the future.
  • And that is why all phones should have replaceable batteries!! 400 cycles that's ridiculous. Windows Phones were and some Androids are doing something to make their phones last a little more than a year!!
  • It is 400 FULL recharge cycles. Charging from 50% is only half of a cycle.
  • I have a L1520 that I wirelessly charge, and in just the last week it will say, "critical battery level - shutting down." However, it does that when there is anywhere from 40-50% charge showing on the battery. I don't know how to re-calibrate the battery. :-(
  • This is a known issue with the 1520.
  • Have always wondered about these types of details surrounding batteries. Thanks. 
  • I usually keep it around the 80 mark so I can afford to just turn off at night and charge it when I get to work. I don't know if this improves longevity but if I'm near chargers all the time might as well use them.
  • I Charger mine only when it hit 30%. Hold a better charge now when it reaches 50% and lower now
  • I can tell you from personal experience that this will quickly kill your battery.
  • Nowhere do you mention that fast charging creates much more heat than normal charging, and hence it damages the battery more. So much for all those reviews that say not to worry about the pathetic small battery in the new flagship skinny phone, you've got fast charging.
  • Not all fast charging technologies generate heat on battery. I use Dash charge on my OnePlus 5T and the battery is cool while the phone is charging. This is because dash charge is not increasing the voltage but the amperage to charge faster.
  • The articles that were quoted were from 2010. We didn't have fast charging back then. While I'm sure the basic science is still relevant, it would have been better to see current information.
  • Live vs worry :D I charge usually overnight (good for maybe 2 days) + when needed. It's easier to use a phone when I don't have to monitor how much juice is still left.
    Also I think that each battery is what it was made to, good or bad, and it cannot be changed much by charging.
    If overnight is too long, put charger into timer and charge 2-3 hours before wake-up time. Bonus point: if battery is not charged to completely full, coulomb counter (I believe they are still using those, tracking charge in and out of battery because voltage level is bad indicator) will eventually lose track of charge level. Discharge phone completely (shuts down / it's been at 3% for an hour and I'm done with it) and charge fully (100% + hour or two).
  • I have wireless charge issues on my L950. If I leave it on the wireless charger over night it will show 60-64% in the morning. After some observation it appears that leaving it on a wireless charger for 4+ hours cuts the juice down incrementally. Does the same thing with a different brand new battery. It charges no problem when plugged in however and holds the charge. Lately even wireless charging for less than 4 hours doesn't give me any significant gains in charging. I have 3 different back covers with wireless contacts and 2 different batteries and no combination produces different results. 
  • Lumia 950 xl battery is a trash for me. I have change 2 of them cause they were the reason for so many reboots and crashes (back screen-not respond) I used to charge about 20-80% but after second new battery I bought, my parents told me they always charging their phones over night and they never had problems with batteries. So now I decided to charging my Lumia 950xl all night and now 6 months later I don't have problem with that new battery.
  • Nice informative article but no need to worry about it. Batteries will degrade no matter what. I think it would be more stressful babying your battery than just charging whenever is more convinient. No way would i not charge at night as i need my phone when i wake up. Babying the battery will make it last how much longer? a month or two maybe? will still have to replace the battery after a year or two anyways depending on how anal you are about its performance compared to when new.
  • This is a non-issue for anything except laptops older than about 7 years, or VERY cheap "throw away" phones and mp3 players.  Batteries in old laptops or cheap stuff continue to cook when plugged in.  Newer laptops (or good phones/tablets/mp3 players, etc.) no longer have this issue.  Batteries stop charging when full.  Period.  Overnight, overweek.   Makes no difference.   What kills the battery is using it so much that it NEEDS charged every day.   At that rate it will need replaced in less than 2 years.   Here's a hint: put it down.  Stop staring at it for 12 hours a day.  I have 4, 5, 7 year old phones/mp3 players/etc. that still work fine.  If you use it that much, then get a tablet to use at home.  Save your phone for when you are out or otherwise away from wifi.   Just having 2 (or more) devices to split up the usage will make the battery in each last that much longer.  I typically go for 3 or 4 days between charges. OTOH, if you get a new phone every year or 2 years, then don't worry about it.  
  • I have two 640xl and three 640 in my house since May 2015. I charge mine every night and my wife charges hers sometimes twice a day. (Pandora all day while she works, kids use it for netflix.) None of them have reached a point where normal usage can't last a day or more. I have noticed by the end of the day I have closer to 10% charge while when new I often had 30% plus. Some days in the beginning I forgot to charge it and I went almost two days. We bought into Windows when I thought they were finally going somewhere good. And these were great phones on their way somewhere exciting. But then, Microsoft, afraid they might actually succeed, abandoned Win10 mobile. This all points to the point that a bigger battery will also last longer because if 400 charge cycles regardless of battery size, and a bigger battery gives you closer to two days, no amount of fast charging can replace that. 
  • What's wrong with my Lumia 950 XL battery? Battery drains in idle (just sitting on the table) from 96% to 64% in 90 minutes and the phone runs quite hot. It is also almost impossible to charge the battery to 100%. The drainage is the same even I have not opened any app after reboot. Hello is not in use. There's no system updates pending or any app being downloaded or updated.  From settings Battery Use measurement tool shows that the most power hungry apps are Mail and Calendar, Edge and Facebook, although all of them uses battery as background service less than 10% (measured period 1 week). The battery use breakdown shows that System takes 23%, Display 63%, WiFi 8% and Cellular 6% and of those 87% in use and 13% in background. The battery should last more than few hours after full charge. Another weird phenomena: I'm having Low storage warnings even there's only one third of the storage space used (9.6 GB used out of 29.1 GB). There's no SD card in use
  • Хорошая статья. Такое надо реализовать на программном уровне с выбором максимального заряда.