1, nominal capacity
There are identification of battery capacity on the shell of the USB power bank, such as 10400mAh. This represents the capacity of the battery. The greater the capacity is, the more charging times for mobile phones would be. The current mainstream USB power bank can have the battery capacity of 10400mAh. But some unscrupulous manufacturers will fill the battery with cement block, or poor battery cells.
2, charging current
The greater the charging current is, the shorter the time would be to fulfill the USB power bank. Generally the charge current in around 1A-2A.
3, discharge current
Greater discharge current does not indicate greater current to be charged to the phone. The charging current to the mobile phone is determined by the charging current of the mobile phone itself. As long as the discharge current of the USB power bank is greater than the rated charge current of the phone, we can ensure that the phone can be charged in accordance with the rated current charge. For example, the charging current of Apple phone is 1A, and it is 2.1A for ipad. If the discharge current of the USB power bank is greater than 2.1A, it is able to normally charge for ipad or Apple mobile phone.
4, input voltage
The input voltage is generally marked together with the charge current, indicating the voltage that the adapter outputs for the USB power bank to charge, whose nominal value is 5V. But poor adapter would cause damage to the USB power bank, with the peak voltage of 8V.
5, output voltage
The output voltage is generally marked together with the discharge current, of which the nominal value is 5V. The output voltage of poor USB power banks may be as low as 4V or instantly up to 12V, which often cause the burnout of the phones.
Efficiency would affect the temperature of the USB power bank and the times the phone can charge. General efficiency of charge and discharge requires to be more than 90%.
7, the type of batteries
The battery cell can be divided into two types: polymer and 18650. 18650 batteries often explode, which is relatively heavy but have lower price. Polymer batteries are relatively safe, with light weight but higher price. In the future 18650 batteries will be gradually replaced by polymer batteries for USB power bank. Choosing polymer battery cell can greatly improve the safety parameter. Take us for an example, our company, SHENZHEN WANSHUNTONG SCIENCE&TECHNOLOGY CO.,LTD COMPANY, are gradually replacing 18650 into polymer and develop DP series such as DP662, DP512, etc, which are selling quite well all around the world.
8, display mode of power
Power generally displays via LED lights, nixie tube and LCD screen. LED lights show more intuitive, but not accurate; nixie tube and LCD screen appear to be more accurate, but currently the quality is not eligible. There exist the phenomenon that when inserting the phone, the battery power would instantaneously change.