Does running your laptop on AC power damage the battery? Should you remove the battery to increase its lifetime? If you own a laptop, these questions have probably crossed your mind before. The short answer to both questions is: most likely yes. Curious to learn why? Continue reading for all the juicy details.
To support my arguments and recommendations made at the end of this article, I have to provide some background information. So let’s start with the basics…
How Does A Laptop Battery Work?
The type of battery found in laptops today is called Lithium-Ion (Li-Ion). In this type of battery, lithium ions are loosely embedded (intercalated) in the porous carbon of the anode (negative electrode). When the battery is used, the ions flow from the anode to the cathode (positive electrode) through the electrolyte and the separator. This process releases energy and results in a discharge of the battery. When charging, energy is applied to make the ions move in the opposite direction. A charge thus forces them to return to the anode.
How Do Lithium-Ion Batteries Age?
Theoretically, this process can go back and forth forever. Practically, however, the lifetime of a battery is limited. What happens is that ions get trapped and are no longer available to flow from the anode to the cathode. In other words, the battery loses capacity over time. In fact, Li-Ion batteries start aging the moment they are produced.
What Causes Lithium-Ion Batteries to Age?
High voltage and Overcharge
Laptops typically have a charge threshold, which prevents overcharging and high voltage. However, constantly keeping the battery at a full charge also is a stress factor that contributes to aging.
Room temperature (21°C / 70°F) or higher temperatures promote chemical reactions, ultimately causing Li-Ion batteries to lose capacity.
Temperatures below 0°C (32°F) can damage materials inside the battery.
Li-Ion batteries self-discharge at a rate of approximately 8% per month at 21°C (70°F). This increases with higher temperatures. When stored over long periods of time, the battery can reach a state of deep discharge (charge below 20%).
Batteries can break.
To Remove or Not To Remove
As indicated in the introduction, the answer is: yes, remove the battery to extend its lifetime!
When you continuously run your laptop on a reliable AC power source, you should definitely remove your battery. Firstly, the battery will not be exposed to heat from your laptop. Secondly, there is not even a remote chance that it will be overcharged or exposed to high voltage. Hence, removing the battery eliminates the two main causes for battery aging.
When I say remove, I don’t mean that you should simply take out the battery. Please turn off your laptop, remove the battery, and then boot your laptop. For safety reasons, please do not remove the battery while your laptop is running.
You can do multiple things. I wrote an entire article on this topic (link above). Below you will find a summary.
Proper treatment of a Li-Ion battery:
- never discharge battery below 20%
- always partially discharge, then recharge
- cycle* battery every few weeks or after 30 partial dis/charges
- charge at lower voltage (if possible)
- never leave charged battery in laptop when running on AC power
* Cycle means that you discharge the battery to around 20% and then recharge it fully. Going below 20% equals a deep discharge, something you will want to avoid.
Preparing a Li-ion battery for storage:
- charge battery to 40-50%
- remove from laptop
- put into an air-tight zip-lock bag
- store in fridge at 4-8
- re-charge to 40-50% every few weeks
When storing your battery, take note how fast it self-discharges and make sure it never goes below 20%.
For times when you have to run your laptop on battery, you should have a look at this article: 20 Ways To Increase Laptop’s Battery Life
What are your experiences with laptop batteries? Do you go through all the hoops to extend the lifetime of your battery?