What do you mean powerbank? It cannot be charged while in use if that is what you are thinking. To just charge in general any powerbank will work, try to find one that is 2.2.amp to minimize charging time.
I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
I go to the slopes for snowboarding and i think my tom tom adventurer doesnt record my runs during all day. I need between some stops to charge my whatch in the mointain. What is the best powerbank light and powerfull?