If you're around
When someone is playing with their phone
Suddenly screamed and stood up
And quickly rush to the power supply
Don't be surprised
Most likely because
His phone sends out a prompt
——
Coming to shut down
There are friends who are curious
Why have mobile phones
When 1% of the battery is left
It can also be used with ease
And there were
Soon it went into shutdown mode
In fact
The remaining battery level displayed by the phone
Not exactly
Battery power
Trying to figure this out
Let's talk about it first
What's going on with the phone battery
1
How does the phone know
How much electricity is left?
We all know that the power supply of mobile phone batteries depends on the chemical reactions that occur in the battery. Theoretically, we can know exactly how much power is left by measuring how much reactant is left.
The process sounds as simple as measuring how much water is in the tank, but it's actually very difficult. Nowadays, there is no way to directly measure the amount of reactants inside the battery, and the power of the mobile phone can only be speculated by detecting some parameters in the circuit.
So we see that the remaining battery displayed on the phone is actually a speculative value.
There are many battery parameters that need to be detected by the mobile phone, and here we mainly introduce two parameters related to the estimated remaining power of the mobile phone.
2
voltage
If you search for mobile phone batteries on the Internet, you may see that many batteries are marked with a parameter - standard voltage (also written as "nominal voltage"), this voltage is generally around 3.7V, but in fact, the lithium battery in the mobile phone does not output this voltage stably from beginning to end when it is working.
The standard voltage marked on the lithium battery (picture source: screenshot of an online store)
For example, this image shows the voltage change of a certain model of lithium battery during discharge. At the beginning of the discharge, the voltage is close to 4.2V, and at the end of the battery discharge, the voltage drops rapidly.
Changes in the discharge voltage of a certain model of lithium battery, image source: reference
Therefore, the mobile phone can also judge the amount of power by detecting the internal battery voltage change. For example, you can define the battery voltage of 4.2V as the full power state, that is, 100%, and define the battery exhaustion state when 3.3V, that is, 0%, and then the mobile phone will automatically shut down (the average mobile phone rarely really uses the battery voltage to 3V).
Based on such a curve, the phone can show us how much battery is left. This method sounds simple and straightforward, but there are some problems.
One of the most obvious problems is that the voltage drop is not a linear process during use, and it can be seen from the curve in the figure that the battery voltage drops relatively quickly when the battery is about to run out. If you strictly follow this curve, it is possible that the battery level will suddenly drop from 15% to 0%, which can cause a lot of trouble.
However, this problem is relatively easy to solve, as long as some corrections are made to the displayed data. In addition, judging the amount of electricity based on voltage alone will face a problem, that is, it will be affected by many factors.
For example, the voltage drop curve is also different under different operating currents. Under the condition of different working currents, the discharge curve of the battery is different, which we call the rate performance, and the following picture is the decrease of the battery voltage under different rate conditions.
Variation of battery voltage at different rates, Image source: Reference
If you are chatting with your mobile phone and the battery current is relatively small, it may be high to estimate the remaining power according to the current situation. When you open the mobile game, the working current of the mobile phone will become larger, and after the mobile phone is re-estimated, you will find that the remaining power is not so high, and the displayed power may change back and forth.
Therefore, in addition to detecting the battery voltage, the phone may also need to check other parameters.
3
Telephone
In the built-in chip of many mobile phones, there is something called a coulomb meter, which can help the phone more accurately determine the remaining power.
Although many people have returned their high school electrical knowledge to physics teachers, I believe that everyone is no stranger to the unit of "milliampere-hour", after all, the battery capacity of mobile phones is used in milliampere-hours (mAh). Generally speaking, the larger the milliampere-hour, the more charge is stored.
The "coulomb" in the name "coulomb" is also a unit of electric charge, and the coulomb counter is able to detect how much charge is released from the battery during use. Subtract the amount of charge that the battery is able to store to know how much power is left.
With the help of a coulomb counter, the phone is also able to make more accurate battery predictions, but even then, there are still errors. Therefore, the remaining amount of power we see is only an estimate, not an exact value.
4
Product Considerations
Since there will be errors in predicting the power of mobile phones, different mobile phone manufacturers will also have their own considerations.
For example, some manufacturers will consider that since the battery level estimate is not so accurate, simply let the phone display 1% as soon as possible, so that users can charge the phone as soon as possible to avoid unnecessary trouble.
Moreover, when the battery is about to run out, many phones will also automatically enter a low power mode, turn down the screen brightness, and stop unimportant programs in the background, which will make the last 1% appear more durable.
There are also some manufacturers that adopt a strategy that allows you to make a 30-second sprint to the charger when the battery enters 2%.
Therefore, some mobile phones can use 1% of the battery for a long time, while some mobile phones can only use 2% for 30 seconds, which is not comparable, and it cannot be said who has the last power to be more resistant.
Source: Science_China