Consumer Council has tested 30 power banks from the market and found serious problems such as lower-than-rated capacity, poor cyclability, shape change after usage, and low fire resistance in a few models (https://www.consumer.org.hk/ws_chi/news/press/491/power-banks.html).
Power banks are ubiquitous nowadays, as people rely heavily on cell phone for communication, work and entertainment. However, there are no regulations on power bank manufacturing, labelling and selling, so the quality of these power banks can vary much. There have been numerous smokes and fires relating to power banks, and safety becomes a big concern.
In fact, it is almost impossible to distinguish by visual inspection whether a power bank is new or old, has the rated capacity or not, or whether its quality is good or bad. A user should pay attention to whether there is any deformation of the device or abnormal temperature rise during use.
There is probably a need to have stricter regulations from the government on power banks. On the other hand, citizens do need to be aware that a power bank is not just a battery, but an electronic device with high energy content, and should take good care of it to prevent damages and short circuit.
Dr. Denis Yu, Assistant Professor (SEE)