Given a flight number, how can one know the maximum capacity (mAh or Wh) and number of external batteries one may have in one's carry-on luggage, without having to contact the airline company or search through their websites?

[Example of external batteries, a.k.a. power banks](https://smile.amazon.com/gp/product/B07TSHW85D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1):

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/hmcI2.png