Most modern phones come with some sort of fast charging capabilities, and you should always try to find a power bank or charger that can accommodate. For example, iPhones support Power Delivery at about 20W, while some Android phones go with proprietary tech that pushes the speed beyond 20W. Check what standard your device uses and find a charger that can keep up. You'll be much happier in the long run even if you spend a few more dollars.