What The Tech?: Battery Trickle

CHARLOTTE – It’s a question almost as old as smartphones themselves. Should you leave a phone on charge while you sleep?

Charging a phone while you’re catching some Zzzzs is convenient. You wake up, your phone is fully charged and you hope it makes it through the day. Does it affect the battery being on charge for 8 hours? It does and here’s why.

Most batteries’ lifespans are counted in charging cycles. The iPhone has about 500 charging cycles before you start noticing a big difference. But Apple counts charges not by the number of times you put it on charge, but by the number of times it totals a full charge. It’s basically true for other phones because they all use the same battery technology.

If it’s on charge at night, the phone stops charging at 100%. But when it hits 100%, it drops back to 99% and then charges to 100% again. That’s called ‘battery trickle’ and it’ll do this throughout the night. Over time, that 1% drop and recharge will total a full charge and it will happen dozens of times each night.

Newer iPhones have a feature where it learns when you go to sleep and adjusts how it charges. You can see it for yourself on an iPhone by looking at the battery settings. You’ll probably see that the phone charged to 80% about an hour after you put it on charge at bedtime. Then, between 4 and 5 AM, just before you wake up, it finished the charge to 100%. You should check to make sure battery optimization is turned on in the battery settings. Android phones don’t have this particular feature but it does have battery optimization which closes programs you’re not using.

You should also check your battery’s health which you’ll also find in the settings. This will show how the battery has aged. Older phones will likely only be capable of using 80% or a little more of what a new battery can deliver.

All that said, what’s the best way to charge a phone? Optimally, charge it to about 88% before you go to bed and leave it off the charger while you sleep. When you wake up, plug it in and charge the battery fully. But if you typically upgrade your phone every year or so, you won’t notice a huge difference, so charge it any way you want.