At one point or another, all laptop users have the same question: Is it bad to leave your laptop plugged in all the time?
It turns out that the answer is not entirely straightforward. So let’s see what it is.
Know the battery of your laptop
There are two main types of batteries used in laptops: lithium-ion and lithium-polymer. Although these are different technologies, they operate in broadly identical ways, producing energy through the movement of electrons.
This constant flow is also necessary to keep the battery healthy.
For both types of batteries, the following statements are true (at least when it comes to modern laptops ):
- A battery cannot be overcharged. There is no danger of overcharging a battery if you leave it plugged in all the time. As soon as it reaches 100%, it stops charging and only restarts when the voltage drops below a certain level.
- Completely discharging a battery will damage it. Allowing the battery to drain completely for an extended period of time can put it in a state of deep discharge. This can be fatal: you may never be able to charge it again. (You can try these methods to suddenly start a dead laptop battery).
So, based on this, should we conclude that you need to leave your laptop plugged in all the time? Not quite.
Things that damage lithium batteries
The truth about lithium-based batteries is that they are inherently unstable. They start to lose capacity as soon as they are produced and many factors accelerate their decline. Among these, we can mention:
- Charge / discharge cycles. Each battery has a limited number of times it can be charged and discharged.
- The voltage level. The higher the charge level (measured in volts per cell), the shorter the battery life.
- High temperature, over 30 degrees Celsius. It can cause irreparable damage.
The last two are the ones that interest us the most here. Comprehensive study shows how high voltage and high temperatures shorten the life of an isolated battery, and even more when combined.
Charge or voltage level
Lithium-ion batteries charge at 4.20 volts per cell, which is 100% of their capacity. At this level, the battery will have a lifespan of 300 to 500 discharge cycles.
Each reduction of 0.10 V / cell in the load doubles the number of discharge cycles, until the optimum level is reached: 3.90V / cell, with 2400-4000 discharge cycles.
Unfortunately, at this level, the battery is only about 60% charged. The autonomy will hardly exceed half of a fully charged battery.
And then there is the heat. High temperatures , generally classified as above 30 degrees Celsius, shorten the life of a battery, regardless of any other factor. Leaving your laptop in your car on a summer afternoon is a bad idea.
When you combine the stress of high temperature with that of high voltage, the effects are even worse.
The study shows that a battery stored with a 40% charge at 40 degrees would see its capacity drop to 85% after a year.
Fully charged, its capacity drops to 65% under the same conditions. For a fully charged battery at 60 degrees, the capacity drops to 60% in just three months.
The evidence seems clear. Keeping the battery permanently charged at 100% will slowly reduce its life. Keeping it at 100% and exposing it to high temperatures will reduce it much faster.
And remember, these high temperatures aren’t just environmental. Resource-intensive tasks, like gaming or video editing, greatly increase the heat level, and using the laptop on a pillow or in a poorly designed case can trap that heat as well.
For the sake of your battery, it’s always a good idea to fix an overheating laptop.
Should you remove the battery?
If heat is such a danger, it raises another question. Should you remove the battery completely when using your laptop on AC power?
Obviously, this is not possible on the growing number of laptops with sealed batteries.
When replaceable, the answer seems to vary from manufacturer to manufacturer. Acer, for example, says you don’t need to remove the battery on AC power, but remove it if you won’t be using it for several days. When Apple produced laptops with removable batteries, it advised against removing them.
It all comes down to configuring the power management in the laptop. Some may reduce power when no battery is available, just as some do when the battery level is low. It could leave you with poor performance.
If you decide to remove the battery, be sure to store it properly. This usually means that it should be 40-80% charged and stored at room temperature.
Should you keep your laptop plugged in?
Does leaving your laptop plugged in damage the battery? Yes it is. But recharging it every day also damages it.
Oddly enough, the industry as a whole doesn’t seem to have come up with a single answer to the question of whether you should use your laptop on AC power or on battery power.
We have seen that Acer recommends removing the battery when not in use. According to Asus , you should drain the battery to at least 50% every two weeks. But Dell says it’s okay to leave the laptop plugged in all the time.
Apple’s advice is no longer on its website, but you can still read it online. The company recommends that you don’t leave a laptop plugged in all the time.
Leaving your laptop plugged in won’t cause any short-term damage, but if you only ever use it on AC power, you will almost certainly find that after a year the battery capacity has been significantly reduced. . Likewise, if you only use it on battery power, you will go through battery drain cycles more quickly.
The best solution is therefore a kind of compromise between the two: use it on battery some days, and keep it plugged in other days. And whatever you do, be careful that it doesn’t get too hot.
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