That phone in your pocket is a modern miracle. Ditto the laptop on your desk, the tablet in your backpack, even the watch on your wrist. And regardless of the capabilities of each, they all have one integral component to thank, one that you probably ought to know how to take care of: a battery.
The first step to knowing your device’s battery is to narrow down the kind. The first kind you might think of (and the kind you probably grew up with) are nickel-metal hydride, or NiMH batteries. These, generally, are the ones that look like normal disposable batteries, except you can plug them into a wall charger for some extra juice whenever your TV remote dies.
The batteries in your modern-day gadgets (fun smartphones to laptops to tablets) are a different animal entirely. These are lithium-ion (aka li-ion) batteries and they have some pretty significant advantages over NiMH and other rechargeable batteries that came before. Lithium-ion batteries are also totally different from straight up lithium batteries, which aren’t rechargeable.
Li-ions can pack a lot of power into a small size, and they don’t lose too much of that energy to leakage when they’re not in use.
How Does a Lithium-ion Battery Work?
All batteries work by having two electrodes (an anode and a cathode) with a bunch of material called electrolyte between. When you plug a battery into a completed circuit, a chemical reaction starts taking place at the anode and electrons start building up over there.
Those electrons want to travel to the cathode, where it is less crowded, but the electrolyte between these two parts keeps the electrons from taking the short way there. The only way through the circuit is the battery, and those electrons power your device in the process.
Meanwhile, the positively charged lithium ions the electrons leave behind travel through the electrolyte to meet the electrons on the cathode side.
Once all the electrons have made the trip, your battery is dead. Except! If you’re using a rechargeable battery like a lithium-ion, you can reverse the process
If you dump energy into a circuit using a charger, you can force the reaction to go in the other direction and get that electron party at the anode all crowded again. Once your battery is recharged, it’ll mostly stay that way until there’s something for it to power again, though all batteries leak some charge over time.
What determines the capacity of the battery (how long it can power your stuff) is the number of lithium ions that can nestle themselves into the tiny porous craters of the anode or the cathode.
Over time, the anode and cathode degrade and can’t fit as many ions as they used to. As that happens, the battery stops holding a charge as well as it once did.
How Does a Lithium-ion Battery Recharge?
It’s easy to think of charging a battery as though you’re filling a tub with “power.” Just hook up the hose until it’s full! From the outside, that’s exactly how it works, but on the inside it’s a little more nuanced.
A lithium-ion battery typically charges in two stages. First comes the process called constant current charging. This is the part that is really pretty simple. The charger for your phone or laptop will apply a steady current of electricity to the battery to get all those electrons back to the anode.
During this stage, the charger just decides how much power is coming out of the firehose and starts spraying. The higher that constant current, the faster the battery can charge. High voltage quick chargers, like on many new phones, take advantage of this first stage to cram in the juice as quickly as possible (at the cost of a bit of extra stress on the battery).
When the battery is 70 percent recharged, the procedure changes and flips over to constant voltage charging. During this second stage, the charger makes sure that the voltage (that is, the difference in current between the battery and the charger) stays the same, rather than keeping the current constant.
Practically, this means that as the battery gets closer to full, the current the charger sends into it decreases. As the battery gets full, the charge simply trickles in, just enough to account for the tiny bit of charge your battery loses naturally over time.
How to Keep Your Laptop Battery Healthy
You want your laptop and smartphone charged and ready to go, but you’ve probably heard that charging puts wear and tear on the batteries in laptops, smartphones, and other portable devices. So where does that leave you? Should you leave the laptop on the charger, let it rundown, or do something else entirely?
First, accept that there’s no perfect solution.
Let’s dig into the ins and outs of laptop batteries. Batteries are ultimately consumables. Just because the battery in your phone or laptop might last years before you need to replace it, doesn’t change the fact that it was never intended to last forever.
It has a finite number of charge cycles, usually between 500 and 1000, and from the moment you start using your device, you’re shortening the battery’s life. In a perfectly optimal scenario, your laptop battery would never be too warm (high temperatures degrade lithium-ion batteries), rarely charged above 80% or discharged below 20%, and you’d never leave it dead in your laptop bag or charging for months at a time.
Battery technology (and the hardware in the laptop that manages the battery) has improved tremendously over the years. Don’t let a bad experience with a laptop ten or 15 years ago color how you use your battery today. We know the laptops we used in the 2000s had terrible battery life no matter what we did, but the laptops today are much more forgiving and have a much longer lifespan. There’s a good chance you’ll replace your laptop before the battery health is degraded.
But, let’s look at things you don’t need to worry about, things you should pay attention to, and some simple tips.
Don’t Worry about Overcharging Your Laptop’s Battery
There is a persistent myth that you can overcharge a laptop battery and, through that overcharging, damage the battery. There are many ways to decrease the lifespan of your battery (like leaving your poor laptop to roast in your car on a hot day) but overcharging isn’t one of them.
Even ancient laptops have built-in protection against overcharging and potential damage caused by packing too much energy into a battery that can’t hold it all. You can certainly damage a laptop with a cheap, out-of-spec or damaged charger, but keeping your laptop plugged in with the original charger or a high quality replacement won’t turn your battery into a lithium-ion fire bomb.
When your battery reaches 100 percent, it stops charging. It won’t resume charging until the battery level drops below 100 percent again. While this can lead to a pattern of the battery discharging slightly and then getting topped off again (which can degrade the battery over time), it won’t overcharge the battery and damage it.
Don’t Let the Laptop Get Too Hot
One of the main factors affecting laptop battery life is temperature. Low temperature can be an issue if you live in a very cold climate, but high temperatures are a much bigger concern.
You not only have to worry about ambient conditions, but heat is also naturally generated by the computer’s processor and other components. You should make sure air can circulate around your laptop, keeping any vents clear and not resting it on a cushion. Try to keep it under 95 degrees Fahrenheit. If you use the laptop in bed, a stand is a good way to keep it cool.
It should go without saying, leaving your laptop in your car on a hot day is a very bad thing.
Don’t Let the Battery Run Down
If you are running your laptop off battery power, you should ideally avoid fully discharging it, or even getting below around 20 percent regularly.
Tests have shown that it can take around 600 complete discharges to reduce a laptop battery’s capacity to 70 percent. By comparison, if you only run the battery down to around 50% before charging it, you’ll get over 1500 discharges before its lifespan is reduced to the same level. You don’t need to wait to see the “charge battery soon” light. Go ahead and keep it above 25% or 50% if you can.
Keep the Battery Charged When Not in Use
The charge level of your battery is important even when you’re not using your laptop.
HP recommends that batteries should be stored with 50-70 percent charge at temperatures between 68-77 degrees Fahrenheit. If you’re not going to use your laptop for a while, try and keep it as close to these conditions as possible.
You should never store a device for a long time with the battery fully run down. You might never get it working again.
Discharge Cycles Can Help “Calibrate” the Battery
Putting your laptop through an occasional full charge cycle (not total discharge as mentioned above) can help calibrate the battery in many laptops. This ensures that 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 percent battery left when its really 0 percent, 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. The 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 leave your laptop plugged in all the time; it might show you incorrect battery life estimate and die before you expect it to.
Should I Keep My Laptop Plugged in All the Time?
At this point, you might be left wondering exactly what you should do with your laptop: leave it plugged in, only plug it in to charge, or some carefully balanced mix of the two with an eye on battery percentages and such.
Unfortunately, there’s not a lot of clear advice on the matter. Many laptop manufacturers simply don’t address the topic with a clear-cut answer (or at all). Apple used to advise against leaving MacBooks plugged in all the time, but their battery advice page no longer has that piece of advice on it.
If you dig around in HP’s help files, you’ll find a Q & A about laptop battery charging where they acknowledge exactly what we’ve talked about here: that charging your battery adds wear, there’s no way to avoid it, and keeping it partially charged significantly extends battery life. Overall, their advice is to charge your battery as little as possible. That’s technically accurate, but a bit impractical in the real world.
Our advice to you, tempered by realistic expectations for what people will actually tolerate and do under real-world conditions, would be to charge your laptop as little as practical for the way you use your laptop.
For example, if you only use your laptop when working away from home (and otherwise use your desktop computer) then it makes sense to charge the laptop to around 70-80 percent and then leave it shut down completely in a sort of storage mode for your next trip to the coffee shop.
If you use your laptop off the charger everyday, then it makes sense to charge it daily to ensure it’s ready to go the next day. You could always opt to take it off the charger after the amount of time it takes to fully charge it or use a smart plug routine to charge it for X number of minutes before turning it off for the day.
But again, to emphasize a point from the beginning of the article, laptop batteries are light years better than they were a decade ago and you’re probably not going to get a huge return on your investment micromanaging your laptop battery.
Finally, if you rarely take the laptop off the charger or use it away from home, it’s probably not worth stressing about elaborate charging routines, and battery optimization strategies. If you have a gaming laptop that sucks down so much power that you pretty much need to keep it plugged in to enjoy it, there is no sense in stressing about the battery health over years of game play.
Your laptop will continue to work, plugged in if the battery health is absolute trash. At that point, it’ll be no different than a desktop computer plugged into the wall for continuous power. And if that’s how you’ve been using it for years, then it hardly matters if the battery isn’t in optimum shape.