charging your phone overnight

Does charging your phone overnight RUIN the battery?

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Does charging your phone overnight RUIN the battery?


Smartphones can fully charge within two to three hours. Normally, people worry about overcharging their phones and think that overnight charging can ruin their devices. This means that many people commonly unplug their power cables before going to bed.

However, there is another category of people who have the opposite opinion – that overcharging of mobiles does not affect the batteries.

Most of the cellphone manufacturers warn not to overcharge the mobile phones, recommending that you cease charging at 100%.

Many of these warnings regarding nocturnal charging are, in fact, superfluous. Most modern cellphones feature a fast charger: the charger recharges the battery in a matter of minutes and once the cellphone is fully re-charged, the charger automatically stops.

Many researchers are still arguing that you shouldn’t charge overnight or overcharge your cellphone. To explain this mystery let’s have a look at reasons why you shouldn’t re-charge the mobile phone overnight.

Lithium-ion Battery

As most of us know, cellphones normally contain a rechargeable lithium-ion battery, commonly known as Li-ion battery. These batteries re-charge comparatively faster than traditional batteries.

Modern smartphones with a fast charging function re-charge the battery up to 80% in minutes. The remaining 20% takes a little longer to recharge.

However, with all the applications running in the background including emails, constant messaging, news updates and notifications, the charge quickly diminishes. Which is why many people consider overnight charging a necessity.

Mobile Apps

Still, we know that a fast charger automatically turns off the power supply to the device when it reaches 100%, but with constant updates on mobile apps, the charger will continue charging the small bit of charge that a mobile phone consumes naturally on its own.

In this situation, the cellphone constantly stays between full charge and a little below. This increases the battery temperature for a prolonged period, which can eventually reduce its capacity. This problem can, of course, be largely avoided if you turn the phone off while you sleep.

Another important reason not to recharge mobile phones overnight concerns the lifespan of rechargeable batteries. The capacity of rechargeable batteries is finite. And over time, it reduces with extensive use.

So the batteries used in mobile devices are in constant decay from the moment they’re first used. The constant recharging of mobile phone batteries results in a steady loss of their capacity.

Battery Lifespan

As the lifespan of the battery reduces, so does the speed with which it accepts the charge. So with every cycle of charging, we increase the amount of time that a mobile phone spends with the charger. In this sense, overnight charging of mobile devices DOES reduce battery life.

With that in mind, research has shown that by keeping the cellphones on charge overnight, we roughly keep them on charge for around three to four months each year.

This constant discharging and recharging increases the number of cycles of every recharge, which ultimately ends the battery life sooner.

Moreover, in order to extend the life span of the battery and to reduce the number of recharge cycles we need, researchers recommend NOT waiting until the device is close to 0% before charging it.

Recharging cycles

The primary reason behind this recommendation is that charging a fully discharged battery increases the number of recharging cycles which ultimately reduces the battery life and its capacity.

The best recharge time for a cellphone, as recommended by battery experts, is when your charge is around 35-40% percent. This won’t consume a full recharge cycle, so increases the battery life.

One of the main issues with Li-Ion batteries is that they are temperature sensitive. Their charge and output efficiency can vary widely depending on the operating temperature of the battery.

The only way that lithium-ion batteries can handle extra incoming current is by dissipating energy as heat. This increases the battery temperature and causes gases within the battery structure. In extreme cases, this can result in the battery rupturing or exploding.

The latest technological advances in the smartphone battery, i.e. cutting off the battery from power once it’s charged, largely eliminates the threat of overheating during the night.


The main circumstance upon which overheating can still be an issue is with, the use of third-party chargers. These are often cheaply made, may not conform to the applicable safety standards, and are probably not compatible with the cellphone and its energy needs. In these cases, the threat of overheating due to the overnight charging is real.

As mentioned earlier, lithium-ion batteries tend to decrease their capacity after charge-and-discharge cycles. To avoid this, it is recommended that the battery’s charge level reaches no lower than 35-40% before plugging in for a charge.

Moreover, for overnight charging so-called ‘fast chargers’ are not recommended because they can cause overheating, thus reducing the lifespan of the battery.

For the modern smartphone, overnight charging doesn’t cause any damage, provided that you are using the original and charger supplied by the manufacturer.

Does charging your phone overnight ruin the battery – the VERDICT

However, any and all charging ultimately eats into the lifespan of the battery. So, by following the instruction above and generally making wise choices with your use of the cellphone, you can manage the decline and squeeze the maximum possible use from your trusty battery.

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Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life.

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