The battery can only be charged 500 times? Don't be ridiculous! This real charging secret is recommended for collection →

Our lives are inseparable from electronic devices, and electronic devices, in turn, are inseparable from batteries that provide them with energy.

There are many "tips to extend battery life" on the Internet, such as "discharge all the power of newly purchased electronic devices before charging them for the first time", "keep your laptop plugged in to protect the battery", "store electronic devices that are not used for a long time with full charge"...

Which of these battery "life extension" claims are reliable and which are not? Today, we will explain them all to you at once.

01

The battery can only be recharged 500 times?

Fake.

There are some sayings on the Internet that "mobile phone batteries can only be charged 500 times before they die", so you should try to reduce the number of times you charge the battery.

This statement is a misunderstanding. A paper published in 2015 pointed out that the service life of lithium batteries is not determined by the number of times they are charged, but by the total amount of charge transferred [1].

This statement may be a bit abstract, and we can understand it through an example.

For example, Apple batteries promise that after 500 "charging cycles", the battery's power limit can still reach more than 80% of the factory state.

Image source: Screenshot from Apple's official website

Apple's official website also gives a clear explanation of the "charging cycle", which can be simply understood as: every time you use up 100% of the power, it is considered a charging cycle (it has nothing to do with how much you use each time or whether you charge in between).

For example, if you use 60% of the battery today, fully charge it at night, and use another 40% the next day, this counts as one charging cycle.

In addition, after the charging cycle reaches 500 times, it does not mean that the battery has reached the end of its life, but the maximum power is affected. For example, Apple batteries will drop to 80% of the initial power, and batteries from other manufacturers will also drop to a certain percentage, but they are not completely unusable.

Therefore, the statement that “a battery becomes unusable after 500 charges” is not reliable.

02

Don't wait until the battery is almost dead before charging?

real.

When the battery power is too low, some changes will occur inside the battery. For example, for lithium cobalt oxide batteries, excessive discharge will cause part of the lithium cobalt oxide to become lithium oxide that cannot participate in charging and discharging, thereby reducing the battery life.

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When lithium iron phosphate batteries are discharged, the lattice size of lithium iron phosphate will change, and excessive discharge will also have an adverse effect on the battery.

So it's true that waiting until the battery is too low to charge is bad for the battery.

As for the “optimal level” for battery charging, different studies have reached different conclusions [1] (ranging from 40% to 60%, 25% to 75%), but one thing is certain: do not wait until your phone runs out of battery before charging; you can consider charging when the battery is around 50% [1].

03

New electronic devices need to use up all the electricity before they can be charged

And enough charge for 12 hours?

Fake.

This saying comes from the early days of the atomic force microscope, nickel-cadmium rechargeable batteries and nickel-metal hydride rechargeable batteries. In particular, nickel-cadmium rechargeable batteries have a significant memory effect. If they are charged multiple times without being fully discharged, the nickel-cadmium battery will remember the low power and reduce the battery capacity.

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Although some studies have found that lithium batteries also have a certain memory effect[2], it is much smaller than that of nickel-cadmium batteries and can be ignored under normal use of electronic devices. In addition, considering the previous point, if the battery is really discharged and then recharged, it will cause greater damage to the battery.

In addition, it is not necessary to fully charge a new battery for 12 hours.

Overcharging will also damage the battery, and now batteries and original chargers generally have anti-overcharge protection. It is completely unnecessary to wait for 12 hours after the battery is fully charged.

04

Will playing with your phone while it is charging damage the battery?

uncertain.

First of all, using your phone while charging it won't harm the battery. It just slows down the charging process (after all, you're using it while charging). But if you're charging it while playing apps that consume more power, such as playing games, it may cause problems.

I believe you must have had this experience: when charging your phone, it often gets a little hot. When playing some power-consuming games, the phone will also get hot. If you play such games while charging, the phone may become hot to the touch.

Mobile phone batteries have an optimal operating temperature. For example, the picture below shows the suitable temperature information provided on Apple’s official website.

Image source: Internet

When the phone becomes hot to the touch, the temperature of the phone will definitely exceed 35 degrees. Charging the battery in this situation will cause damage to the battery.

Therefore, when charging your phone, sending and receiving messages or browsing your Moments will not have any effect on the battery. However, if your phone becomes hot while you are charging it while playing games or watching videos, it may damage the battery.

05

Will leaving your phone charger plugged in overnight damage the battery?

uncertain.

Mobile phone batteries and original chargers generally have overcharge protection. They will stop charging after the battery is charged to 100%, or only provide a very weak current to make up for the battery's own consumption. In this case, there will be no damage to the battery.

However, it should be noted that if you use a charging head produced by an informal manufacturer, there may be a risk of overcharge protection failure, which may damage the battery.

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In addition, if the phone is placed in a place that is not easy to dissipate heat when charging, such as under a pillow, in a quilt, or covered with a phone case that is not easy to dissipate heat, the battery may overheat, which may cause damage to the battery.

Therefore, use a charging head produced by a regular manufacturer, place the phone in an environment where heat can be dissipated normally, and there is no problem leaving the charger plugged in all night (after all, no one wants to set an alarm to get up in the early morning to unplug the charger).

06

Can the laptop be left plugged in all the time?

real.

Like mobile phone batteries, today’s laptop batteries also have overcharge protection, so there is no need to worry about overcharging your computer battery.

Moreover, when the power supply is plugged in, the power supply can directly power the computer without going through the battery, so it is equivalent to not using the battery when the power supply is plugged in.

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Although the power supply will automatically recharge the battery after the battery power is naturally depleted, the battery cycle life occupied by this is very small, and is almost negligible compared to unplugging the power supply and using the battery directly after it is fully charged.

Therefore, there is no need to unplug the power cord when using a laptop.

It should be noted that although keeping the laptop battery fully charged for a long time is not the most ideal state, compared to unplugging the power supply every time to fully charge and use the battery, leaving it plugged in will not cause too much damage to the battery.

07

Do you need to charge and store electronic devices that are not used for a long time?

correct.

Some electronic devices may not be used as frequently as mobile phones, such as idle tablets, or cameras that are only taken out occasionally to take pictures.

If these electronic devices are left unused for a long time with their batteries depleted, it will indeed affect the battery life and maximum capacity.

Therefore, before storing these devices, they need to be charged , but the fuller the charge, the better.

For example, HP's official website recommends charging the battery to 80% to 90% before long-term storage, and checking and replenishing the battery every three months[3].

Apple's official website recommends charging the battery to about 50% for long-term storage and recharging it every 6 months[4].

Image source: Internet

Therefore, the recommended charging levels for different electronic devices when they are stored may vary, but one thing is certain: do not store the battery in a depleted state, otherwise the maximum battery capacity may be affected.

I hope the above can help your battery "extend life".

References:

[1] de Vries H, Nguyen TT, het Veld B O. Increasing the cycle life of lithium ion cells by partial state of charge cycling[J]. Microelectronics Reliability, 2015, 55(11): 2247-2253.

[2] Sasaki T, Ukyo Y, Novák P. Memory effect in a lithium-ion battery[J]. Nature materials, 2013, 12(6): 569-575.

[3] https://support.hp.com/us-en/document/c01297640

[4] https://www.apple.com.cn/batteries/maximizing-performance

Author｜Science Scraps Popular Science Team

Review | Li Quan, PhD, Institute of Physics, Chinese Academy of Sciences

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