Weight is a real, simple test
A genuine higher-capacity power bank has real battery cells inside and noticeable weight for its size — a suspiciously light unit claiming a high mAh rating is a red flag.
Check the actual output, not just capacity
A high mAh number means little if the output amperage is low; look for the actual watt or amp rating printed on the device itself, not just the marketing capacity figure.
Safety certifications should be visible
Legitimate power banks display safety certification marks on the device itself; their complete absence is worth treating cautiously, especially on unusually cheap listings.
Real-world charging test
A genuine power bank should charge your phone close to the number of times basic math on its capacity suggests — a unit that charges your phone only a fraction of what\’s advertised likely has a real capacity far below what\’s printed on the box.