Should you leave your laptop plugged in and charging when you’re not on-the-go? What’s best for the battery? It’s a tough question, and there are quite a few contradictory recommendations out there.
It’s important to understand the basics of how the standard lithium ion (Li-ion) and Lithium polymer (LiPo) batteries in modern devices work. There are a lot of battery myths out there.
There’s no way to “overcharge” these batteries. When you get to 100% charge and leave your laptop plugged in, the charger will stop charging the battery. The laptop will just run directly off the power cable. After the battery discharges a bit, the charger will kick into gear again and top the battery off. There’s no risk of damaging the battery by charging it over its capacity.
Your laptop battery will always wear down over time. The more charge cycles you put the battery through, the more it will wear down. Different batteries have different ratings, but you can often expect about 500 full charge cycles.
That doesn’t mean you should avoid discharging the battery. Storing the battery at a high charge level is bad for it. On the other hand, letting the battery run down to completely empty every single time you use it is also bad. There’s no way to just tell your laptop to leave the battery at about 50% full, which might be ideal. On top of that, high temperatures will also wear down the battery more quickly.
In other words, if you were going to leave your laptop battery in a closet somewhere, it would be best to leave it at about 50% charged capacity and make sure the closet was reasonably cool. That would prolong the battery’s life.
Here’s one clear thing: Heat is bad. So, if your laptop has a removable battery, you may want to remove the battery from the laptop if you plan on leaving it plugged in for a long time. This will ensure the battery isn’t exposed to all that unnecessary heat.
This is most important when the laptop runs very hot—like a powerful gaming laptop running demanding PC games, for example. If your laptop runs fairly cool, you won’t see as much benefit from this.
Of course, many modern laptops don’t have removable batteries anymore, so this tip won’t apply in those cases.
Ultimately, it’s not clear which is worse for a battery. Leaving the battery at 100% capacity will decrease its lifespan, but running it through repeated discharge and recharge cycles will also decrease its lifespan. Basically, whatever you do, your battery will wear down and lose capacity. That’s just how batteries work. The real question is what makes it die more slowly.
Laptop manufacturers are all over the place on this. Apple used to advise against leaving MacBooks plugged in all the time, but their battery advice page no longer has this piece of advice on it. Some PC manufacturers say leaving a laptop plugged in all the time is fine, while others recommend against it with no apparent reason.
Apple used to advise charging and discharging the laptop’s battery at least once per month, but no longer does so. If you’re concerned about leaving your laptop plugged in all the time (even if it’s a PC laptop), you might want to put it through a charge cycle once per month just to be safe. Apple used to recommend this to “keep the battery juices flowing”. But whether this will help depends on the device and its battery technology, so there’s really no one-size-fits-all answer.
Putting your laptop through an occasional full charge cycle can help calibrate the battery on many laptops. This ensures the laptop knows exactly how much charge it has left and can show you an accurate estimate. In other words, if your battery isn’t calibrated properly, Windows may think you have 20% battery left when it’s really 0%, and your laptop will shut down without giving you much warning.
By allowing the laptop’s battery to (almost) fully discharge and then recharge, the battery circuitry can learn how much power it has left. This isn’t necessary on all devices. In fact, Apple explicitly says it’s no longer necessary for modern MacBooks with built-in batteries.
This calibration process won’t improve the battery’s lifespan or make it hold more energy—it will only ensure the computer is giving you an accurate estimation. But this is one reason you wouldn’t to leave your laptop plugged in all the time. When you unplug it and use it on battery power, it might show you incorrect battery life estimates and die before you expect it to.
Your laptop’s battery isn’t going to last forever, and it will gradually have less capacity over time no matter what you do. All you can do is hope your laptop’s battery lasts until you can replace your laptop with a new one.
Of course, even if the capacity of your laptop’s battery declines, you’ll still be able to keep using it while plugged into a power outlet anyway.
Image Credit: Intel Free Press