Given how paranoid many of us are about keeping our smartphone batteries going until we can find a charging socket in the nearest coffee shop, train or bus, it’s perhaps understandable that the also-not-insignificant matter of the batteries in our laptops is sometimes overlooked.
We all want our laptop batteries to last for as long as possible, of course. But there are also many unhelpful myths circulating about them, as shown by the popularity of ‘leaving laptop plugged in’ and ‘can you overcharge a laptop’ Google searches by those seeking the truth.
So, what is the truth? As is so often the case with matters like this, the answer’s a bit more complicated than you might initially presume.
No, you can’t overcharge a laptop
Phew! It’s good to get that one out of the way.
You see, although there are two main types of batteries used in laptops – lithium-ion and lithium-polymer – and these are distinctly different technologies, the way they work is actually broadly the same. In both cases, it’s the movement of electrons that creates that much-needed power, with this flow also instrumental in preserving the health of the battery.
The important takeaway point here, though, is that you can’t ‘overcharge’ either type of battery. Even leaving a laptop plugged in once it has reached 100% charge will just mean the charger stops charging the battery.
As a result, the laptop will be left to run directly off the power cable, and once the battery has discharged a bit, the charger will kick back into gear to keep the battery topped off nicely.
So if leaving the laptop fully charged isn’t an issue… what about discharging?
We’re not saying you should absolutely never do this. In fact, it can be a good thing to do once in a while, as it helps your battery to more accurately estimate how much juice it has left, compared to if you left it on 90%-plus charge all of the time. As a matter of fact, leaving your battery on a high charge isn’t great either, as far as longevity is concerned.
The problem is that any laptop battery has a finite number of charge cycles, and the more of these cycles you put it through, the more worn-down it will become. The situation differs from one battery to another, but as a rough guideline, about 500 full charge cycles is typical.
In an ideal world, then, you’d probably keep your battery charged at around 50% – although of course, that’s hardly the easiest or most convenient thing to do.
What other factors should I worry about?
The short answer: heat. Temperatures of more than 30 degrees Celsius have been shown to cause irreparable damage to batteries and shorten their lifespan.
If you store the battery at the same temperature but at a charge of 40%, though, it’ll only lose a quarter of its charge holding capacity over an entire year.
So, there you have it – if you want to keep your battery in optimum condition for longer, the best advice is probably to store it in hospitable temperatures charged at the 50%-ish mark, as tricky as that might be.
So, can I leave my laptop plugged in all of the time?
As we touched on above, your battery will wear down over time, regardless of what you do.
Nonetheless, Battery University’s tests have found that a battery charged to 100% will only have about 300 to 500 discharge cycles, compared to the 1,000 to 2,000 discharge cycles that are possible if you keep it charged between 70% and 80%.
It’s therefore clear that avoiding either of the two obvious extremes – not keeping your laptop fully charged all of the time, but also not completely discharging it – is generally the way to go.
When you combine this approach with a commitment to keeping your laptop battery below 30 degrees Celsius, you stand the best chance of enjoying the maximum lifespan from the battery.
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.
You Can’t Overcharge the Laptop’s Battery
RELATED: Debunking Battery Life Myths for Mobile Phones, Tablets, and Laptops
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.
All Batteries Wear Down Over Time [For a Few Reasons]
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.
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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.
Remove the Battery to Avoid Heat, if You Can
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.
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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.
But Should I Leave It Plugged In or Not?
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.
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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.
Occasional Discharge and Recharges Can Help “Calibrate” the Battery
RELATED: How to Calibrate Your Laptop's Battery for Accurate Battery Life Estimates
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.
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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