It’s a murky aspect of gadget ownership: lithium batteries are finicky. They all gradually lose capacity, which means it’s only a matter of time before your device simply isn’t carrying enough juice to be useful. But how long? Some of this is built into the design, but how we charge and use batteries can also make a difference.
For example, leaving your device plugged in most of the time can help you avoid the stress of being caught with a low battery. But it could also stress your battery.
So what can we do to extend battery life? I called two scientists who study lithium batteries, Gregory A. Keoleian of the University of Michigan and Michael G. Pecht of the University of Maryland. “The main factors influencing degradation are temperature, state of charge and rate of charge,” says Keoleian.
They advised us to always follow the specific advice of the manufacturers. (For the record, here’s what Apple and Samsung are saying.)
But the scientists also shared some useful general tips on how charging habits can help our batteries live long and happily.
1) Don’t charge until you’re at 20%
To get the most out of your lithium battery life, your goal is to slow down the rate at which you burn through the so-called charge cycles. All devices are designed and manufactured with a target number of times the battery can be fully discharged and recharged. It is usually between 300 and 1000.
So here’s a rule of thumb: don’t start charging until your battery reaches around 20% and try to stop when you reach around 80%. This will ensure you maximize every cycle while keeping the battery stress-free. (Keep reading for details on how some smart devices like iPhones handle this for you.)
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“It’s best to charge right before you use it, that’s ideal,” says Keoleian.
It’s also true that the slower you charge, the less damage you do to the battery. These days, some products are sold with “fast” charging capabilities when using special bricks or car charging stations. Speed is obviously great when you’re in a hurry, but Pecht says you should avoid it when you don’t need it.
2) Don’t leave it plugged in at 100% – or let it go to zero
Many of us charge devices overnight while we sleep, which is fine. But we also plug them in so the reader can commute to work or a desk all day. “Avoid keeping things plugged in 24/7,” says Keoleian, as this can cause your battery capacity to drain.
The reverse is also true: being completely drained is stressful on your battery, so avoid draining your battery to zero if you can.
And forget a myth that sometimes you have to completely discharge and recharge to clear the battery’s ‘memory’. This applies to lead acid batteries, but not the lithium ones that most mobile gadgets use today.
Pecht recommends storing devices that you won’t be using for a while, such as a power drill, at around 50% charge. This means that it’s also not a good idea to leave items in their magazines when you’re not using them for a while. (We’ll see laptops in docking stations below.)
3) Don’t let it get too hot
Like most of us, our batteries are happiest at 72 degrees or lower. And it’s especially bad for battery chemistry to be exposed to heat over 90 degrees, like in a car on a hot summer day. “Remember that when a battery is enclosed in a case, it can get even hotter,” says Pecht.
Cooler temperatures (above freezing) aren’t as bad, although some manufacturers advise against charging in extreme cold. Pecht says he stores unused batteries in the fridge – just make sure they’re not exposed to moisture which could corrode the electronics around the battery.
4) Don’t get too obsessed with charging with a newer phone or laptop
Good news: Over the past decade, products including high-end smartphones and laptops have become much smarter about charging and automatically avoid some of the mistakes above.
Many laptops, which can stay in docking stations for weeks, now know to stop charging and keep the battery below 100%, although Keoleian says it’s still a good idea to unplug it from time to time.
Apple iPhones running iOS 13 or later have a nifty feature called Optimized Battery Charging that can follow your typical routine and automatically time the charge to make sure it’s full just before you wake up and wake up. you had to start using it.
5) Don’t upgrade when the battery runs out – fix
When your device’s battery finally runs out, you don’t necessarily need to get rid of it. Ask the manufacturer if there’s a way to replace the battery – or even see if you can do it yourself using a repair website such as iFixit.
Getting a few more years out of an existing gadget will save you money, and it’s also much better for the environment.
Ask the Help Desk: What questions do you have about the technology in your life?