Charge batteries to last longer


Your charging habits can kill your gadgets.

After a recent column about the hidden death dates built into our devices, many Washington Post readers asked me what we can do to extend the life of products with rechargeable batteries.

“I have an Apple phone that I usually charge once a day, when the battery reaches 50 percent or less,” emailed Marian Levine of Silver Spring, MD. “Will it extend battery life if I wait until the battery is low?”

It’s a cloudy aspect of owning gadgets: lithium batteries are finicky. They all gradually lose capacity, meaning it’s only a matter of time before your device just doesn’t have enough juice to be useful. But how much time? Some of this is baked into the design, but the way 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 getting caught with a low battery. But it can also put a strain on your battery.

So what can we do to make batteries last longer? 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,” Keoleian says.

They advised us to always follow the specific advice of manufacturers. (For the record, here’s what Apple and Samsung say.)

But the scientists also shared some helpful general tips about how charging habits can help our batteries live long, happy lives.

Washington Post tech columnist Geoffrey A. Fowler shares five ways to conserve battery life and keep your devices out of landfill. (Video: Jonathan Baran/The Washington Post)

1) Don’t charge until you drop to 20 percent

To get the most out of your lithium battery, your goal is to slow down the rate at which you burn through so-called charge cycles. All devices are designed and manufactured with a certain number of times the battery can be fully discharged and recharged. It is usually between 300 and 1,000.

So here’s a handy rule: don’t start charging until your battery reaches about 20 percent — and try to stop when you’re about 80 percent. This ensures that you maximize each cycle while keeping the battery voltage free. (Keep reading for details on how some smart devices like iPhones do this for you.)

Is your battery swelling like a balloon? This is why.

“It’s better to charge right before you start using it — that’s the ideal,” Keoleian says.

Also, the slower you charge, the less damage you do to the battery. Today, some products are sold with “fast” charging capabilities when you use special bricks or car charging stations. Of course, fast is great if you’re in a hurry, but Pecht says you should avoid it if you don’t need it.

2) Don’t keep it plugged in at 100 percent – or let it go to zero

Many of us charge devices at night while we sleep, which is fine. But then we also plug them in for the ride to work or at a desk all day long. “Avoid leaving things plugged in 24/7,” Keoleian says, as that can drain your battery’s capacity.

The reverse is also true: being completely drained puts a strain on your battery, so avoid draining your battery if possible.

And forget about a myth that says you need to fully discharge and recharge every now and then to clear the battery’s “memory”. That’s true for lead-acid batteries, but not for the lithium batteries that most mobile gadgets use today.

Pecht recommends putting away about 50 percent of devices you won’t be using for a while, such as an electric drill. This means it’s also not a good idea to leave things in their charger if you’re not going to use them for a while. (We get to 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 cooler. And it’s particularly bad for battery chemistry to be exposed to heat above 90 degrees, like inside a car on a sweltering summer day. “Remember that when a battery is in a case, it can get even hotter,” says Pecht.

Cooler temperatures (above freezing) aren’t too bad, although some manufacturers advise against charging in extreme cold. Pecht says he keeps unused batteries in the fridge — just make sure they aren’t exposed to moisture that can corrode the electronics around the battery.

4) Don’t worry too much about charging with a recent phone or laptop

A bit of good news: Over the past decade, products including high-end smartphones and laptops have gotten much smarter at charging and automatically avoid some of the above errors.

Many laptops, which can be docked for weeks at a time, now know to stop charging and keep the battery below 100 percent — although Keoleian says it’s still a good idea to unplug it every now and then.

Apple iPhones running iOS 13 or later have a handy feature called Optimized Battery Charging, which can follow your typical routine and automatically time the charge to make sure it’s full right before you wake up and need to start using it.

5) Don’t upgrade if the battery is dead – fix it

When your device’s battery finally runs out, you don’t necessarily need to remove it. Ask the manufacturer if there is a way to replace the battery – or see if you can do it yourself using a repair website like iFixit.

Getting a few more years out of an existing gadget saves you money, and it’s much better for the environment, too.

Ask the help desk: What questions do you have about the technology in your life?

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