Mobile power has now become a must for smartphone users, but do you know the real situation of mobile power? Not long ago, a friend asked the author that he bought a 6000mAH power bank, which claims that the conversion efficiency can reach 90%, but why the iphone6S is not fully charged three times? Is it a fake bid?

We know that the battery capacity of iphone6S is 1460mAH. According to the simplest arithmetic, 6000÷1460≈4.11, that is to say, 6000mAH should be fully charged 4 times, but why is the actual situation so far different?

Let’s talk about the conversion efficiency of mobile power. Let me briefly explain the charging principle of the mobile power supply. At present, the built-in battery (18650 and polymer) of the mobile power supply has a nominal voltage of 3.7V, while the standard input voltage of digital products such as mobile phones is 5V. Therefore, the mobile power supply needs to output 5V through the boost management board to charge mobile phones and other devices. The actual power after the boost conversion is shown in the above figure. According to the law of conservation of energy, a 6000mAH mobile power supply has a battery energy of 6000mAH×3.7V=22.2Wh (watt hour). After the boost is converted to 5V, the overall energy remains unchanged , But the power is 22Wh÷5V=4400mAH, which is like pouring a cup of 3.7 liters of water into a 5-liter cup. After the first conversion, only 74% of the original 6000mAH power is left. This 4400mAH is actually the power that can be supplied to the mobile phone. The various losses during charging are followed by connecting the mobile power supply and the mobile phone with a data cable for charging. Then the question arises again. Can all the 4400mA power reach the battery of the mobile phone? The answer is of course no. During the charging process, there are still many losses in these power levels:

1. Circuit conversion loss. I believe everyone knows that the mobile power supply generates heat when charging. According to the law of conservation of energy, the heat emitted is actually the energy of the built-in battery.

2. Resistance loss. When charging the mobile phone, the built-in battery of the mobile power supply and the mobile phone battery are connected through a circuit board and a wire. We know that all conductors have resistance, and there is no conductor with zero resistance (superconductors are not in the scope of this discussion). The main physical characteristic of the resistor is to convert electrical energy into heat. Therefore, during the charging process, the conductor will generate heat, and if the heat is generated, there will be energy dissipation and loss.

3. Voltage loss. The discharge voltage of a lithium battery is not static, and the safe range of the discharge voltage is 4.2V-2.7V, and there will be differences in the power conversion. Generally, the discharge voltage range is between 3.6-3.9V, and 80% or more of the battery's power can be discharged, and if it is outside this range, the power loss will increase.

4. Power supply loss. When charging a mobile phone, the mobile power supply not only charges the battery, but also supplies power to other components, especially the screen is a big power consumer.

5. Own operating loss. During the charging process, the mobile power supply also consumes power to maintain its own operation, and the power is also supplied by the built-in battery. Through the above losses, the power that actually reaches the mobile phone battery is about 85% of the actual power of 4400mAH, which is 3774mAH. From the cell capacity of 6000mAH to the actual output power of 3774mAH, approximately 38% of the power was lost during this period. In other words, the actual conversion efficiency is only about 62%. Next, the author attaches two pictures to tell you how many times a 6000mAH mobile power bank can charge a mobile phone. 6000mAH mobile power actual charging times 6000mAH mobile power actual charging times Through the above explanation, I believe everyone should understand that the efficiency of mobile power in practical applications is actually not high. The mobile power that everyone usually buys is basically at this level, and it does not reach more than 90% of the advertised by some manufacturers. As far as dozens of mobile power products reviewed by the author, most of the conversion efficiency is between 60%-63%, and occasionally when the materials and workmanship are better, the conversion efficiency is only 70%. Therefore, after reading this article, we must have a clear understanding of the actual conversion efficiency of mobile power so that we can have a deeper understanding of mobile power.