A friend had his powerbank confiscated at the Beijing airport because it has no marking stating the capacity (must be one of those homemade powerbank!). There was a whole box full of confiscated powerbank at the airport. This probably applies to other airport in china as well.
The rules on a piece of paper handed over by the security stated that you can only carry on if it is clearly marked with value <20000mAH x 5V or < 100wH. For those between 20000mAH to 32000mAH (100wH - 160wH) you have to declare and check in. Actually the rating allowed is very high, most powerbanks are much lower!
Not sure if there is any similar rules in place elsewhere?Edited: 5 years ago