Most people who use a laptop on a regular basis, tend to leave it always connected to the power for long periods of time. Is this bad for the durability of the battery? In this article we are going to demystify the myth and explain what happens when you leave your laptop always connected to the power.
In the past, the usual rule of thumb when using laptops for long periods of time was to remove the battery and leave them plugged into the mains so that the battery would not lose its durability.
However, nowadays it is common for laptops to have an integrated battery and it cannot be easily removed and replaced without having to disassemble them. Is this rule still valid?
Is the battery overloaded?
If you have a laptop and you always have it connected to the power supply, it is likely that at some point you have been given several typical and often contradictory pieces of advice: Should you disconnect it from the power supply so that the battery can make charging cycles and thus improve its durability?
In some cases, some people think that if you leave the laptop plugged in with the battery fully charged, the battery may overcharge. Don’t pay any attention, this will never really happen because that’s why they have protection mechanisms.
Maybe in older laptops – really old ones, in fact – this could happen, but for many years now laptops have had hardware protection systems that will prevent the battery from overcharging.
In general, when the laptop detects that the battery is at 100% it will stop charging the battery and, using a relay similar to the one in a UPS, will redirect external power directly to the laptop. In other words, it is as if we had removed the battery and, therefore, it will never overcharge.
How much does the laptop battery degrade?
Unfortunately, batteries degrade over time whether you have the laptop connected to power or not. In fact, the battery will degrade even if you remove it and do not use it.
For this reason, you may have the false feeling that, if you have had the laptop connected to the power for a long time and then you want to use it with the battery, the battery has a shorter autonomy than when the equipment was new.
But this is normal, and the reason is not because you have had it connected to the power supply, but because batteries degrade.
How much does the battery degrade? As always, it depends. However, there is a table below from Battery University (does this exist? Yes, it does) that analyzes how batteries degrade over time when they are stored, unused, with a specific percentage of charge for a period of one year.
As you can see, if you store the battery at 100% charge at 25ºC ambient temperature for a year, it will degrade 20% of its total capacity, while if you store it at 40% charge, the degradation is only 4%.
This means that if you are going to remove the battery from the laptop, it is better to do so when it is not at 100% charge, as it will degrade much more slowly. In addition, degradation is more noticeable when the battery is subjected to a high temperature, so try to keep the laptop as cool as possible.
Studies show that after 300-500 cycles the battery performance starts to drop, which means that the battery life will be shorter.
Therefore, the first year we will obtain almost the maximum of the useful capacity of the battery, which will begin to reduce with the passage of this.
Take this data as a reference, not as something categorical. This is because there are different batteries with different technologies. There are batteries of more capacity, with a different construction process, etc.
How can we measure the life of the battery?
We must pay attention to the “State of Charge”, which is a percentage of maximum capacity. Also, we can see it expressed as “Depth of Discharge” or depth of discharge, which is another percentage of the maximum charge.
To check the battery status of our laptop, we must do the following:
- Open the start menu and type “cmd” to run “Command Prompt”.
- Now, type the following command: “powercfg/batteryreport”. You will get this message: “The battery life report has been saved to path X”.
- Go to the path and open the .html file. It will show us a log of our battery usage.
If you don’t like the idea of having to enter commands, you can always download BatteryInfoview, a very light portable program that shows us the most important data. In this case, we will not have a history as in the other option, but we can see the most important data, such as the charge cycles.
In any case, as you have seen there are many different and free ways to see the state of the battery, and even if some of them are not completely accurate, they are useful to get an idea of the state in which it is and if it needs some maintenance or not.
So, do I always leave the laptop plugged in or not?
In view of the data provided, the best thing you can do to preserve the durability of the battery is that if you are going to keep the laptop always connected to the mains, remove the battery when it is approximately 40% charged and, every so often, connect it to charge it to 100% and let it discharge to 40% before removing it again and putting it away.
If your laptop does not have the possibility to remove the battery, then it is recommended that you do some “maintenance”, and at least once a month you remove the cable to let the battery discharge to 20% – this is what Battery University says – and then charge it to 100% again.
In any case, as you may have noticed from the table above, heat is one of the biggest enemies of batteries, so when you remove and store it, it is advisable to do so in a cool, dry place, in fact the cooler the better.