Now on the market portable source There are many kinds of mobile power supplies. When we select mobile power supplies, we often compare the parameters of mobile power supplies, in addition to their appearance and portability. So, what are the main performance parameters of mobile power that deserve attention? Xiaoji makes a summary here:

Capacity (mAh): The power of rechargeable batteries is milliampere hour (mAh), which is the product of current intensity and time. When the current intensity is in milliampere (mA) and time is in hour (h), their multiplication is milliampere hour (mAh). It indicates the time of complete discharge under a certain discharge current. For example, 1000 milliampere hour means that the battery can discharge for 1 hour under 1000 milliampere current.

The capacity division of mobile power supply is not too strict. Generally, the capacity of mobile power supply is about 1000mAh to 12000mAh. Considering that the battery capacity of mainstream smart phones is generally about 2000mAh (for example, the battery capacity of Xiaomi M2 is mAh, and that of Samsung i9300 is 2100mAh), we divide mobile power supply into less than 2000mAh by capacity (one-time charging, considering portability) , 2000-5000mAh (capable of charging mobile phones for 1-2 times), 5000mAh - 10000mAh (capable of charging mobile phones for multiple times or tablet computers) and above 10000mAh (capable of charging multiple devices), and different models of mobile power sources in these four levels will be evaluated in the subsequent evaluation.

We should also point out that for mobile power, the larger the capacity, the better. After all, the capacity is only a parameter that can measure the use time. When purchasing, you should choose according to your own usage habits and actual needs, and you should never blindly pursue "large capacity".

In addition, it is worth noting that the capacity of the mobile power supply generally refers to the capacity value marked on the outer package of the product by the manufacturer. This capacity value generally refers to the capacity value of the internal cell of the mobile power supply, rather than the capacity value that many consumers think can be used actually.

Output voltage (V): Simulated computer USB port and mobile phone charger, generally 5V;

Output current (mA): At present, the common output current standards are 500mA, 1000mA (1A) and 2100mA (2.1A). The former two are generally used to charge mobile phones, while the latter is commonly used to charge tablet computers with large capacity mobile power. Like the capacity, the output current is also an important index to be considered when selecting the mobile power supply. This is because, under the same voltage, the current more similar to the nominal parameters of the charged equipment can make the charging process more efficient. As for the influence of different output currents on the charging efficiency of equipment, Love to play computer games It will also be verified in subsequent tests.

Input voltage (V): Simulated computer USB port and mobile phone charger, generally 5V;

Input current (mA): Similarly, the output current of mobile power supply directly affects the charging efficiency of digital products, and the input current of mobile power supply also directly affects the charging efficiency of mobile power supply. For example, if the rated input current of a 12000 mAh mobile power supply is only 500 mA, it means that it takes more than 20 hours to fully charge the mobile power supply; But if the rated input current is 2.1A, it only takes about 7 hours, that is, the time to sleep at night.

[caption id="attachment_20176" align="aligncenter" width="680"] 12000mAh large capacity power supply of a brand with rated input current of 2.1A [/caption]

Conversion rate (%): Generally speaking, the conversion rate of the mobile power supply is the conversion efficiency of the charge and discharge of the internal cell of the mobile power supply. For example, theoretically, if a 5000mAh mobile power supply is charged with a 5V/1A cross current power supply, it can be fully charged in 5 hours, but in fact, this is impossible. This is because there will be some losses in the process of charging and discharging, including:

• L Circuit conversion loss;
• L Self running loss;
• L Boost loss; wait.

The boost loss is the reason why we feel that the capacity of mobile power supply is not as large as we thought. The discharge voltage of the lithium battery cell used in the mobile power supply is generally about 3.7V-4.2V, while the standard input voltage of digital products such as mobile phones is 5V, so the mobile power supply needs to output 5V voltage through the internal boost circuit to charge the mobile phone, which will also cause losses.

In short, the so-called "capacity" only represents the discharge capacity of the mobile power supply under the nominal voltage output and the specified current, but it does not really represent the real energy of the mobile power supply. The energy of the battery is expressed in watt hours (Wh), which is the product of the capacity (mAh) and the rated voltage (V). For example, for a 5000mAh mobile power supply, the capacity here is the capacity of the lithium battery cell, and the rated voltage is 3.7V, so its energy should be 5000mAh * 3.7V/1000=18.5Wh. However, if it is output after boosting to 5V, its effective output power is 18.5Wh/5V * 1000=3700mAh, This is why we may find in use that a mobile power supply with a nominal capacity of 5000mAh may not be able to charge an iPhone 5 with 1440mAh for three times.

The conversion efficiency of the cell directly determines the quality of the mobile power supply. Generally speaking, the discharge conversion rate of imported cells is 85%, and that of domestic A products is about 75% - 85%.

The above are only some of the main performance parameters that can help users to select mobile power, but the mobile power market is mixed, and there are also many phenomena such as false labeled capacity and parameters. When purchasing, you should not only pay attention to the parameters, but also pay attention to the use experience of others.

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