Can I leave my smartphone charging all night?

We tell you how the smartphone’s battery is arranged, what determines its service life and how to charge it properly.

From the very moment that mobile phones have become part of our lives, humanity has been plagued by a charging problem. We have become so dependent on electronics so much that the very thought of a draining battery causes panic. To remain without communication in the middle of the working day, to lose at once both contacts, and the navigator, and access to the network - is this not a horror?

Many people charge their smartphones before going to bed and sleep peacefully all night, knowing that in the morning the indicator will show 100%. But for users who are accustomed to taking care of technology, this approach raises a bunch of questions: is it not harmful to leave the phone plugged in when it is already charged? Could this lead to a battery explosion or a shortened battery life? Is there any way to extend the battery life? A lot of dubious rumors go to this account on the Internet.

What is the truth? Let's find out from the experts.


How does a mobile battery work?

Today, mobile devices use lithium-ion batteries. They contain two electrodes. One of them is graphite, the other is lithium cobalt oxide. Between them is a liquid electrolyte that allows lithium ions to move between the electrodes. When the smartphone is connected to the charger , the ions begin to move from a positively charged electrode (lithium cobalt oxide) to a negatively charged electrode (graphite). When discharged, the movement is in the opposite direction.

Speaking about battery life, it’s wrong to use the terms “month” or “year”. The same battery can last one person for several years, and another for only six months. It all depends on the intensity of operation, that is, on how often the battery has to be charged.

Therefore, the battery life is measured not by habitual time units, but by charge-discharge cycles. One cycle implies the consumption of full capacity - from 100% to 0%. In practice, this rarely happens: usually a portion of the charge is consumed in one day, for example, 60%, then the smartphone spends the night on charge, and the next day another 40% is used until the cycle ends. The smartphone’s battery is designed for 500-600 such cycles, after which the degradation process becomes noticeable.

Degradation is a phenomenon in which the battery loses its ability to hold a charge, that is, its actual capacity decreases. For example, after 500 charge-discharge cycles, the iPhone battery will retain only 80% of its original capacity: it was 2800 mAh and 2240 left. It is very difficult to miss such a change in the smartphone.

Degradation is a normal occurrence. You cannot completely stop it, but you can slow it down. Any battery loses its properties over time, however, how quickly this process will occur depends on many factors. If you handle the battery with care, signs of a decrease in battery capacity will not bother you for very long.

What affects battery life?

“Battery life is largely dependent on the increase in resistance inside it,” explains Professor of the Department of Energy Jan Shao-Horn of the Massachusetts Institute of Technology. “The constant maintenance of the charge at a high level increases the speed of the so-called parasitic reactions, which leads to an increase in voltage inside the battery.”

The same applies to complete discharge. This phenomenon accelerates internal chemical reactions, which causes the battery to degrade faster. However, the processes of charge and discharge are far from the only thing that affects the battery life.

“There are other factors,” recalls Shao-Horn. - For example, high temperature. It also accelerates parasitic processes. "

Excess heat leads to destruction of the liquid electrolyte. Another factor negatively affecting battery life is charging speed. Fast charge is a popular and very popular feature. Today, when choosing a smartphone, many buyers are interested in whether it supports any of the fast charging standards, and prefer the device in which there is such an option.

“If you don’t go into details, the essence is this: the faster the charging process, the faster the battery wears out,” says Shao Horn. Nevertheless, the professor notes that this problem is more related to electric vehicles and hybrids, which require much more electricity than smartphones to work.

Can I leave the smartphone on charge all night?

Smartphone for that and smartphone (smart - smart): it is able to determine the moment when the battery charge reaches its maximum value, and stop the current supply. Similarly, it turns off when the lower limit is reached.

“The battery cannot be undercharged or overcharged,” explains Daniel Abraham, senior fellow at the US Argonne National Laboratory in Chicago, in an interview with Digital Trends.

Special controllers act as current limiters: they determine the upper and lower thresholds of the battery charge. In other words, their task is to prevent a dangerous situation when more current is supplied than the battery can accommodate, and not allow the battery to discharge to zero.

So if you leave the smartphone connected to the power outlet all night, it is unlikely that this will seriously affect the battery, because when it reaches the maximum charge level, it will simply stop charging. But when the charge drops below 100%, charging will resume. The worst part is that night charging extends the time at which the battery is fully charged, and this potentially accelerates its degradation. The degree of such harm is difficult to assess, since manufacturers implement power management in different ways and use different equipment.

“The quality of the materials used also affects the performance of the battery and its life,” Abraham emphasizes. “The proportion is right here - how much you pay, you get so much.”

Apple, Samsung and other major manufacturers offer recommendations for extending the battery life, but none of them directly says: you can or cannot leave your smartphone on charge all night. Digital Trends employees turned to Apple and Samsung to clarify this question, but have not yet received an answer.

How to charge the smartphone correctly?

If you charge your smartphone as little as possible, you can delay the signs of degradation, and the battery will last longer.

Most experts agree that it is best to maintain a charge level between 20 and 80%. A couple of short recharges during the day do less harm than one long night. As for the Quick Charge technology and the like, it makes sense to resort to this function as little as possible.

What mistakes do we make when charging a smartphone and how to avoid them?

Try not to overheat. Do not drop your smartphone on the dashboard in a car where it can become hot under the sun. To reduce the risk of iPhone overheating, Apple recommends removing the case while charging. Samsung warns that “fully draining the battery will shorten its life,” and advises keeping the charge level above 20%.

It is not worth using the phone when it is charging, as in this case it will be very hot. If the smartphone had to be left to charge for the night, first turn it off to reduce the load on the battery.

Quality accessories - the key to safe charging

Give preference to the chargers and cables that came with the smartphone. If they are lost or out of order, purchase branded ones from the same manufacturer.

It may not be a cheap purchase, but it is definitely worth it. Third-party accessories certified by Samsung or Apple may be a more cost-effective alternative. If you are going to buy a non-native charger, make a choice in favor of well-known brands.

Before buying, you need to make sure that the charger and cable have the right characteristics. To do this, you need to know the current strength and charging power of your smartphone.

Remember: the cheaper the accessory, the more risks. Budget products often do not meet safety criteria, and the consequences of their use can be sad. Last case: in September, a teenage girl died in Kazakhstan. She fell asleep listening to music on a smartphone that was charging at that time. By morning, the battery exploded. What exactly caused it - a poor-quality accessory, improperly organized charging or something else - is unknown, but this tragedy once again reminds that electricity is not a toy, and operating rules are written in order to comply with them.


As you can see, putting the phone in charge all night is very undesirable. But the reality is that it is not always possible to recharge a smartphone during the day. The risks of prolonged night charging can be reduced under two conditions: you use an original charger and do not allow the gadget to overheat.

Remember the basic rules:

  • Always use official chargers and cables or their certified alternatives from well-known brands.
  • Do not let the smartphone overheat (leaving it to charge overnight, remove the cover, do not put under the pillow, do not cover with a blanket).
  • Try to keep the charge in the range of 20-80%.
  • Avoid discharging completely.
  • Use fast charging when there is a real need for it.
  • Limit the use of the smartphone when it is charging (at least do not run graphically demanding applications).