Should I keep my laptop plugged in all the time?

The biggest question when using laptop batteries still has no satisfactory answer, even from the manufacturers themselves.

There are many ways to increase the battery life per charge, such as closing background applications or reducing screen brightness. But what can you do to improve the battery life? Should you regularly unplug the charger to use the battery?

Let's look at this question from both a scientific perspective and the advice of major manufacturers.

Understanding laptop batteries

There are two main types of laptop batteries: lithium-ion and lithium-polymer. While there are differences, they work in the same way: electricity is created when electrons move. The flow of electrons keeps the battery healthy.

With both types of batteries mentioned above, you need to note the following two points:

- Laptop batteries cannot be damaged when left plugged in for too long:When you charge the battery to 100%, the battery will automatically cut off power and will not continue charging until the battery level has dropped to a certain level (e.g. 95% or 98%).

- Leaving the battery in a discharged state will damage the battery:If left at 0% for too long, the laptop battery will fall into a "dead" state and may never wake up.

Based on these two things, can we conclude that keeping your laptop plugged in all the time will keep the battery safe? The answer is "not that simple".

What will damage lithium batteries?

Lithium batteries are inherently unstable and will therefore continually lose their maximum capacity from the moment they are manufactured. There are many factors that can cause lithium batteries to fail prematurely, including:

- Maximum number of charging cycles: Each lithium battery can only be charged a certain number of times.

- Charge level: The higher the charge level (in volts/cell), the shorter the battery life.

- High temperature: Temperatures of 30 degrees Celsius or higher will damage laptop batteries.

The two things we need to pay attention to above are the charge level and the temperature of use. Both of these factors can damage the battery when acting separately or in combination.

Optimal charging level

Each cell in a lithium battery typically reaches a maximum charge of 4.20 volts, which is equivalent to 100% of its capacity. At this level, a laptop battery will last between 300 and 500 charges.

Relationship between charge level (left) and number of charge cycles (middle). Charge level determines the achieved life compared to the maximum battery life in percent.

Every 0.10 volt/cell decrease doubles the number of charge cycles but reduces the battery's storage life. The optimal charge level you will achieve is 3.92V, allowing the battery to "survive" 2400-4000 charge cycles. Unfortunately, at this level the battery life is only about 58%, meaning the usage time is only slightly better than when the battery is half full.

Temperature

Regardless of other factors, operating temperatures above 30°C will shorten battery life. Leaving your laptop battery in a car or a hot room during the summer is obviously a bad idea.

When combined with high charge levels, the effects of temperature on batteries are exacerbated. Tests have shown that batteries stored at 40% charge at 40°C will have a lifespan reduced to just 85% within a year.

Maximum % charge level of 40% and 100% maintained by the battery when stored at different temperatures for 3 months.

Under similar conditions, a battery charged at 100% will have its battery life reduced to 65% within 1 year. Under normal conditions (25°C), a lithium battery charged to 100% will have its battery life reduced to 80%.

The principle here is quite clear. When removing the battery for storage, you should not leave it at 100% and you should also absolutely avoid high temperatures.

More worryingly, the temperature of actual use will also damage the laptop battery. Heavy tasks such as playing games or editing videos will cause the temperature to increase, not to mention poor heat dissipation design or placing the laptop on a pillow will also reduce battery life.

Should you remove the battery while charging?

If temperature is so important, we need to consider another issue: should you remove the battery while charging your laptop?

Oddly, each manufacturer has a different answer. For example, Acer recommends that you always remove the battery when using a laptop plugged in. Dell insists that it’s okay to leave the battery plugged in. HP falls somewhere in the middle, recommending that you only leave your laptop plugged in once every two weeks.

Although Apple no longer produces MacBooks with removable batteries, it has advised users to combine battery use (removed from the charger) with using the charger, to "keep the battery current flowing." According to Apple, constantly plugging in the charger is harmful.

While manufacturers may differ, if you leave your laptop plugged in all the time, you won’t notice any short-term damage, but at 100% battery level, after a year your battery life will definitely decrease quite a bit. Conversely, constantly using your laptop without the charger will also cause the number of charge cycles to decrease significantly after a short time.

So the final answer is somewhere in between: you should charge it at certain times (in the office, in the classroom) and use it at other times (on the train, in the living room). If you are sure that you will never need the battery, you can charge it to 40% - 70% and store it in a cool environment. In any case, be careful not to use the battery when the laptop or room temperature is high.

According to VnReview