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Is It Harmful To Keep Laptop Plugged In?

Is It Harmful To Keep Laptop Plugged In?
The advent of lithium-ion batteries has revolutionized the area of laptop design. Smaller more compact batteries, in concert with innovations in semiconductors and microprocessors, contribute to more compact and lighter-weight laptops. Lithium-ion batteries have improved energy density, power capacity, and better cycle life. But is it bad to keep your laptop plugged in all the time? What is the proper way to charge your laptop's battery? This article will plug you in to the lithium-ion technology in modern batteries today.

Is It Bad To Leave Your Laptop Plugged In All The Time?

The short answer is 'no' it's not bad to leave your laptop plugged in all the time.
But there is more to the story when discussing lithium-ion batteries.
We have to take into account several factors and there are best practices to know to achieve optimal battery life.

First, let's talk about:

What type of battery is in a laptop?

Most recent models of laptop use battery chemistry known as lithium-ion.
  • Li-ion batteries when compared with older chemistry is lighter in weight, have a higher energy density, and last longer or have better cycle life.
  • Unlike the older nickel based battery cells, lithium-ion batteries do not have a 'memory-effect'. This means over their lifespan, they can be partially discharged and then recharged without losing capacity.
  • Typically, Li-ion batteries have a lifespan of about 300 to 500 charge cycles, which is generally about 2 to 3 years. After this point the capacity drops to under 80%.
  • Batteries normally self discharge even with no power draw. Lithium-ion cells typically discharge about 1.5% to 2% per month.
  • Lithium-ion is very sensitive to overcharging, over-discharging, as well as overheating. Most battery packs have a circuit to monitor the voltage and the current, as well as a temperature sensor, to keep it in the safe range.
  • Li‑ion batteries charged in a temperature range of 5 to 45 °C (41 to 113 °F) have shown to be more efficient.
  • Lithium ions flow inside the cells. Gradually, in very simple terms, these ions get 'clogged' in internal anode structures as part of normal operations. After some buildup, there is increased resistance to the flowing ions and this results in decreased battery capacity.

Does It Matter if Your Laptop Is Always Plugged In?

Once the battery of your laptop is fully charged it will stop. Keeping it plugged in to a charger will not cause an issue.
Having said that, best practices for Li-ion battery longevity say a partial charge is better than a full charge. To optimize you battery:
  • Keep it as close to a 50% charge as possible. Every time the battery is cycled it wears down, so avoid deep-cycling and keep it topped off as needed. 
  • Cycling the lithium-ion battery from fully discharged to fully charged routinely will reduce it's life.
  • Heat is harmful to battery cells so keep or store in moderate temperatures as stated above.
The table below shows that the smaller the discharge, or lower DoD, results in a longer battery life.
To maximize Li-ion battery capacity, partially discharge and partially charge, and keep the battery at a moderate temperature range.
Depth Of Discharge

100% DoD
80% DoD
60% DoD
40% DoD
20% DoD
10% DoD
Note: 100% DoD is a full cycle; 10% is very brief. Cycling in mid-state-of-charge would have best longevity.

How do I maximize my laptop battery life?

Laptops affect battery life in many ways, such as, LCD brightness, power management settings and running programs. In the real world you use your laptop and plug it in to charge when needed. Usually, you leave it plugged in until the battery is at 100 percent.

While convenient, this is less than optimal for the lithium-ion battery.
If you're curious about best practices to maximize battery life, there are several steps to follow.
  • As stated above, a partial charge and discharge is better than a full charge and full discharge.
  • Temperature plays a role in lithium-ion battery longevity. A moderate temperature is best, too cold or too hot impairs the battery performance.
  • If you are going to store the lithium-ion battery for some reason, make sure to charge to about 50% and don't let it fully discharge.
Occasionally, the battery percent gauge or 'fuel gauge' might be inaccurate or show the wrong percentage of battery left. This sometimes happens in older batteries.
In this case, to reset and re-calibrate the gauge:
  • Run the laptop until it displays 'low battery' to fully discharge the Li-ion battery.
  • Then fully charge the battery to 100%. This will reset some flags that assist in accurate readings. This process might be occasionally needed but will affect the longevity of the battery. 
Lithium-ion batteries with age will degrade in performance and take longer to charge. Taking the steps above will prolong the useful life of the battery, so you can get the most out of it.

Some laptop manufacturers such as Lenovo have a safeguard chip which authenticates with Lenovo systems. This means if you need to buy a replacement battery, make sure it is compatible and authorized to work in your Lenovo laptop.

Is It Bad To Leave Your Laptop Plugged In All The Time?

How can I improve my laptop's battery life in Windows 10?

Windows 10 has a battery saving power mode called Battery Saver.
By default the Battery saver will automatically turn on when the battery power falls below 20%. Some background applications and push notifications will be limited in this state.
To see or adjust this setting, go to Settings > System > Battery saver.
From the battery saver screen, you can also see what applications are using the most power. Find and select the Battery Use link. You can adjust the battery use screen to display selected time frames.

How do I check the health of my laptop battery?

Some laptop manufacturers, like Lenovo, have applications that will check the health of the laptop's battery. For Lenovo, the application is called: Lenovo Vantage.
If your looking for additional Lenovo Diagnostic tools see this article.
If you are running Windows 10, there is a battery status check you can run.
It is called Battery Check and is run under Command Prompt.
  1. Right click on the start menu
  2. Select Windows PowerShell(Admin)
  3. In the window type in: powercfg /batteryreport
  4. This will generate a report detailing the laptop's battery.

What's the takeaway?

Lithium-ion batteries have been a great advantage for laptops. Both in performance over older batteries but also in smaller size and capacity. Laptop users normally just plug in their computers when low on power and don't ever think about lithium-ion chemistry and battery life. That's okay, but to achieve peak performance and longevity from your battery, follow a few simple steps listed above. You may not always be able to follow the best practices but try to find a workable balance so you can get the most out of lithium-ion battery technology.

READ NEXT: Why Does My Laptop Overheat?


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