Why You Shouldn’t Always Charge Your Phone to 100%
August 9, 2025
source: Pixabay
For most, you have the same pattern at night: brush teeth, plug in phone, and crash. In the morning, it will be sitting there at 100% like a good little soldier, waiting to start the day. That feels obvious, right? Full battery = fewer charging breaks, simple as that. Except… the battery researchers will tell you it’s not that simple.
Don’t get me wrong, hitting 100% isn’t going to fry your phone during the night. Today’s phones are smart enough to stop actively charging when they reach 100%. There are some good reasons, particularly if you’re the type of person who keeps a phone for four, five, even six years, to consider how often you subject it to that top-of-the-tank routine.
What causes batteries to degrade, even if you’re careful
Your phone almost certainly has a lithium-ion battery. These batteries are lightweight, deliver a considerable amount of energy relative to their size, and can be charged hundreds of times. The rub? Each time you use the equivalent of 100% of the capacity of the battery (in one single use or combined use over several days), that is registered in the battery’s memory as a cycle. Batteries only have a limited number of cycles before they start to hold less charge. If you’ve noticed that an older phone that used to last the whole day suddenly dies in the middle of the day and needs a charge, you’re not imagining things. It’s just the battery aging.
The problem with hanging out at 100%
Again, it’s not dangerous, and it’s not instant death for your battery. But lithium-ion batteries don’t like extremes. Regularly discharging to zero is bad for them; so is keeping them topped off at max for hours and hours.
At 100%, the voltage in the battery is higher, and keeping it at 100% for extended periods of time increases the chance of the little chemical changes happening in the battery which eventually decrease capacity. At 100%, it is a bit like stretching a rubber band to the limit and just holding it. It will be fine at first, and then it will just lose its snap.
What the experts say
Seriously, people who know batteries sometimes give this good range of 20%–80%. If you can keep your charge in this comfortable range most of the time, the battery will live a happier life. That doesn’t mean that you never go to 100%. Travel days, long work event days, or some situations where you will be without a charging outlet for hours lend themselves to a 100% charge. The important piece of advice is to not make “always full” your default.
Phone manufacturers are in on this too. Apple’s “Optimized Battery Charging” will halt at roughly 80% and only complete the charging just before you typically wake up. Samsung, Sony, and a few others have similar options hidden in their battery menus.
About this overnight charging habit
Concerns about “overcharging” and ruining their battery by charging their phone while they sleep are still relevant for many people. But that concern went away years ago. In fact, most (if not all) phones pretty much stop charging all together when they reach 100%. Now, the more worrisome thing is the battery sits at 100% for most of the night. If you’re trying to get the most battery life, that’s not good.
If you are worried about battery life, by all means, charge it late afternoon, but unplug it when you go to bed, or use the battery optimization features to prevent 100% until right before you get up. But let’s be real, for most individuals, one or two extra hours of capacity is not the same as waking up to find your battery at 100%.
Small changes that actually work
Start charging at 20–30%, not the “1%” panic point.
Unplug at 80–90% if you know you’re not going to need all the juice that day.
Use your phone’s battery care settings if it has them.
Watch the heat — heat kills batteries faster than almost anything else. So maybe don’t charge your phone on the sunny dashboard of your car in July.
You don’t have to make charging a science project. Phones are designed to operate in messy, imperfect, real world rhythms, not lab conditions. But if you are the type who wants to maintain a device long term, letting the battery experience an easier life – even just a little here and a little there – can add significant value as time goes on.
Consider it like giving your phone a breather from always operating at 100%. You will has plenty of charging capacity to meet your daily needs, and in three or four years’ time, you may just be surprised how long it takes to start asking for an outlet.