I bet this is an interesting topic. Many people have been topping the phone at 100%, charging overnight, drain until it turns off, etc. some people also cited the gizmodo article about how to take care battery in the "right way", which itself is confusing and misleading at times.
Here, let me introduce to you what the data says and how to really, really prolong your battery life.
All the data are from batteryuniversity.com, in fact, I am copying many of their words and figures. Go check this page out if you want to know more How to Prolong Lithium-based Batteries - Battery University
Li-Ion battery has no memory effects, so you can charge it at any battery level, unplug from charger at any battery level. Each battery has limited numbers of cycle of discharge before it's capacity drops below certain threshold. Its the number of cycles that is used as an indicator of the battery life.
Li-Ion battery's life cycle is reduced if the battery is under stress:
These data lists, under various conditions, how many discharge cycles a battery can go through before dropping its capacity below 70%. Stress conditions include higher (>30C) temperature, higher voltage and deeper discharge. Therefore, the following conditions prolong battery life:
1. reduce the depth of discharge (DoD), which means not running battery all the way to 0%, that would be 100% DoD.
2. reduce the temperature of the battery, install a battery monitoring app, and put your phone down a bit when its hot, also don't leave it in the car in the summer sun.
3. reduce the voltage of the battery.
Lets look at the relationship of #3 and charging habit.
charging process composed of 4 stages, the first stage is a very fast charging, charger applies a constant ~4v voltage to the battery, the battery cell's voltage rise quickly to about 4.1v. At the end of this stage, the battery level should be around 90%. The second stage is saturation charge, this pushes the battery cell's voltage to 4.2v (100%), this process is slow, unlike stage 1. Stages 3 and 4 are just so called smart charging, it periodically checks battery cell's voltage, and top it back to 4.2 v.
so 4.2v is 100% battery. by charging it to 100% and keep it at 100%, the battery cell's voltage is forced at 4.2 v, and the battery is under stress, its life cycle is reduced (see first figure above). There are vendors giving options for users to set 100% at 4.1, or 4.0v, this bypass the saturation charging stage entirely and reduce the battery stress, therefore prolong the battery life.
So, my personal suggestion is to charge between 30-80%, that is, charge the phone when its around 30%, and charge to 80% only. You may or may not be able to do that with a smaller battery to start with.
One thing to pay attention to, is that system may not properly report battery level if you don't charge to to full. This can occur every 30-40 cycles, which may be 1-2 month. If your find the battery level way off on the phone, do a calibration, which involves charging the phone to 100%, discharge to 10%, then charge back to 100%.
Here, let me introduce to you what the data says and how to really, really prolong your battery life.
All the data are from batteryuniversity.com, in fact, I am copying many of their words and figures. Go check this page out if you want to know more How to Prolong Lithium-based Batteries - Battery University
Li-Ion battery has no memory effects, so you can charge it at any battery level, unplug from charger at any battery level. Each battery has limited numbers of cycle of discharge before it's capacity drops below certain threshold. Its the number of cycles that is used as an indicator of the battery life.
Li-Ion battery's life cycle is reduced if the battery is under stress:
These data lists, under various conditions, how many discharge cycles a battery can go through before dropping its capacity below 70%. Stress conditions include higher (>30C) temperature, higher voltage and deeper discharge. Therefore, the following conditions prolong battery life:
1. reduce the depth of discharge (DoD), which means not running battery all the way to 0%, that would be 100% DoD.
2. reduce the temperature of the battery, install a battery monitoring app, and put your phone down a bit when its hot, also don't leave it in the car in the summer sun.
3. reduce the voltage of the battery.
Lets look at the relationship of #3 and charging habit.
charging process composed of 4 stages, the first stage is a very fast charging, charger applies a constant ~4v voltage to the battery, the battery cell's voltage rise quickly to about 4.1v. At the end of this stage, the battery level should be around 90%. The second stage is saturation charge, this pushes the battery cell's voltage to 4.2v (100%), this process is slow, unlike stage 1. Stages 3 and 4 are just so called smart charging, it periodically checks battery cell's voltage, and top it back to 4.2 v.
so 4.2v is 100% battery. by charging it to 100% and keep it at 100%, the battery cell's voltage is forced at 4.2 v, and the battery is under stress, its life cycle is reduced (see first figure above). There are vendors giving options for users to set 100% at 4.1, or 4.0v, this bypass the saturation charging stage entirely and reduce the battery stress, therefore prolong the battery life.
So, my personal suggestion is to charge between 30-80%, that is, charge the phone when its around 30%, and charge to 80% only. You may or may not be able to do that with a smaller battery to start with.
One thing to pay attention to, is that system may not properly report battery level if you don't charge to to full. This can occur every 30-40 cycles, which may be 1-2 month. If your find the battery level way off on the phone, do a calibration, which involves charging the phone to 100%, discharge to 10%, then charge back to 100%.
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