Anker PowerCore Edge
Since the purchase I am still very satisfied with this energy bolt!
I left it in the drawer for months without using it and only occasionally checked the charge level (self-discharge is very low). So I hardly used my smartphone during the day and a lighter and smaller energy bar for emergencies was enough for recharging.
Most of the time, this big heavy power bar is used in the summer months when there are many thunderstorms and I want to make sure that no lightning strikes damage the expensive hardware when recharging the iPhone batteries.
Update June 24, 2020:
Since today the anchor PowerCore Edge is used more often again. In the beginning only at home, when all sockets and USB ports on MacBook Air are occupied, later also when I'm on the road in a café.
Tip for on the road: Backpack!
The bundle of energy is most comfortable to carry in a backpack, because the weight is hardly noticeable.