One of the key issues of mobile phones, particularly smart phones, is that they are power hungry causing their battery doesn’t last long. As a result, mobile power bank comes into the market as portable external power source to supplement the internal battery of the mobile phone or mobile device.
While most of the modern mobile devices nowadays are using Polymer Lithium ion Battery as their power source, a lot of mobile power banks are using the cylindrical or prismatic Li-Ion battery.
The major problem or hazard of NiMh battery and Li-Polymer battery is that, they will overheat when charged for long time. There is an overcharge prevention IC on its circuit board to cut off the charging when the battery is fully charged. If the IC is malfunctioned, the battery might caught fire or explode when overcharged.
Another disadvantage of Li-Ion battery is their lifespan will greatly reduce if they are operating in high temperature of 45°C and above. Li-Polymer battery, on the other hand, has higher endurance to high temperature, and can still operate over 4 hours in 85°C without much problem.
Nowadays, you can find a lot of power banks claimed to have charge capacity as high as 12000mAh, 18000mAh, 20000mAh, or even higher. If they are unbranded and selling at a very cheap price, you need to be alerted before placing your order.
Branded made-in-Japan one normally has capacity of at least 3100mAh, and comes with one year warranty. They have higher price too and won’t be chosen to make the cheap power bank selling in the Internet stores.
Branded made-in-Korea one is quite reliable too. Part number could be ICR18650-30A, ICR18650-28A, ICR18650-26F, ICR18650-26D, ICR18650-24E, ICR18650-24F, ICE18650-22F, etc. 30F means capacity is 3000mAh, 22F means capacity is 2200mAh, and so on.
Samsung OEM made-in-China Li-Ion battery has 4 grades. The highest A01 grade normally reserved for Samsung own use, while A02, A03 and A04 are made available for customers. Part number could be ICR18650-20, ICR18650-22, ICR18650-24, ICR18650-26, etc. If a power bank claimed to use Samsung batteries, the batteries inside are probably the A02~A04 type.
Certain unbranded made-in-china battery were found to have only 1600-1800mAh but also put in the 18650 battery and claimed to have 3000mAh. The cheap power banks probably are using this kind of Li-Ion battery.