For optimized battery life, your phone should never go below 20 percent or never above 80 percent. It may put your mind at ease when your smartphone's battery reads 100 percent charge, but it's actually not ideal for the battery.
Do not fully charge or fully discharge your device's battery — charge it to around 50 percent. If you store a device when its battery is fully discharged, the battery could fall into a deep discharge state, which renders it incapable of holding a charge.
Once the battery is full, the iPhone begins releasing a minute amount of its charge so it can continue receiving a charge without being damaged. Once the indicator says 100 percent, you can unplug it at any time.
So, the trick: Don't let your phone's battery drain completely to zero, and when charging it, only let it reach about 85 percent and then unplug. If you do fill your battery completely, don't leave the device plugged in; doing so constantly can cause your electronics to age faster in the long run.
It is always recommended by experts to start charging your iPhone when it hits 25 percent. Similarly, only charging the battery up to 85 percent will help the iPhone's battery to maintain good battery health and deliver extended battery life.
If you charge your iPhone overnight, that means it remains at 100% charge for hours on end. This is bad and will accelerate battery aging. To fix this, the Optimized Battery Charging feature on your iPhone prevents it from charging past 80% to reduce some of that stress.
For optimized battery life, your phone should never go below 20 percent or never above 80 percent. It may put your mind at ease when your smartphone's battery reads 100 percent charge, but it's actually not ideal for the battery.
The golden rule is to keep your battery topped up somewhere between 30% and 90% most of the time. Top it up when it drops below 50%, but unplug it before it hits 100%. For this reason, you might want to reconsider leaving it plugged in overnight.
Android phone manufacturers, including Samsung, say the same. “Do not leave your phone connected to the charger for long periods of time or overnight." Huawei says, "Keeping your battery level as close to the middle (30% to 70%) as possible can effectively prolong the battery life."
Only Charge to 85% to Optimize Battery Life
As most lithium-ion batteries' capacity to hold maximum charge gets reduced after 500 charging cycles, Protect Battery may decrease the aging process and increase the battery's operational life span.
Thankfully the easy way is fine
You'll probably have a new phone before that happens. Charge your phone when it needs to be charged and if you end up charging until it reads 100% you don't have anything to worry about, whether wireless or wired. Make sure you use approved cables and chargers it will be fine.
This rule says that when charging your phone's battery, you should only charge it between 20% and 80%. In other words, you should never let your phone's battery go completely dead (below 20%) or completely full (over 80%).
A new, 100%-80% capacity iPhone battery can hold a charge for 8-20 hours, depending on how it's used. Sitting off in your pocket, it can last all day. Playing games and movies, it will last about a third of the day without a power source.
You can charge when it's at 40% and disconnect when it reaches 80%, or any other values, without hurting the phone. The Best Practice, however, is to charge the phone overnight, every night.
To preserve the lifespan of your iPhone battery, Apple has created a battery optimization feature in iOS 13 that slows down how quickly your iPhone charges and will even hold it at 80% to avoid overstressing the battery. That's why your phone sometimes charges all the way, but other times gets stuck at 80%.
The battery will gradually lose capacity, and is rated to remain above 80% capacity (that's total capacity, not charge level) for 500 full charge cycles for an iPhone (1,000 for an iPad).
Don't let it fall below 20% (or higher) and avoid fully discharging the battery unless calibration is needed. Unplug at battery level between 80% (or lower) and 100%. Don't let your phone stay at 100% level for too long, i.e., plugging to charger after fully charged.
Charge Regularly
Unlike the nickel batteries used in older phones, lithium-ion batteries do best when kept above a 50 percent charge. Repeatedly allowing the battery to drain fully may shorten its life and decrease its overall capacity.
Avoid charging beyond 80 percent
Contrary to popular belief, you should not charge your iPhone 100 percent. While this used to work for older batteries, it is not ideal for lithium-ion batteries. They do not come with memory to calibrate, as such; they'll overheat once they hit 100 percent.
It is safe. The sweet spot is 40% to 80%. If you stay in this range the battery lasts the longest. At 100%, the battery is subject to damage from heat, so if you charge it to 100% and then leave it in a hot car, it is not safe.
Stop Charging to 100 Percent Every Time
As a good practice, you should avoid charging your iPhone to 100% all the time and not let it go below 25%. Ideally, keep the battery percent somewhere between 30% and 80% to maintain your iPhone's battery health.
What percentage should I charge the battery to? For regular use, we recommend keeping your car set within the 'Daily' range bracket, up to approximately 90%. Charging up to 100% is best saved for when you are preparing for a longer trip. You can adjust how full the battery charges from the charge settings menu.
When should I charge my phone? The golden rule is to keep your battery topped up somewhere between 30% and 90% most of the time. Top it up when it drops below 50%, but unplug it before it hits 100%. For this reason, you might want to reconsider leaving it plugged in overnight.
If you charge your iPhone overnight for eight or so hours, that stresses it more. Even with optimized charging, the battery is still taxed after it reaches 100 percent, so by leaving it charging overnight when it doesn't need it, you're putting undue strain on the battery.