We drained 5 power banks to see how much of the printed capacity you actually get
The number on the case is real. It is just not measuring the thing you assumed it was.
Daniel ReidMobile editor
A 20,000 mAh power bank does not put 20,000 mAh into your phone. Every one we tested delivered between 60% and 70% of its printed figure, and that is not a scandal. It is physics plus a labelling convention.
Why the number shrinks
The cells inside run at 3.7V and your phone charges at 5V or more. Converting between the 2 loses energy as heat, and the printed capacity is measured at cell voltage rather than output voltage. Roughly a third disappears before anything reaches your phone.
- Fast charging loses more than slow charging. Heat is the tell.
- A cold bank delivers less. Winter is not your friend here.
- Capacity fades with cycles, same as any other battery.
Multiply the printed figure by two thirds and buy against that. You will never be disappointed again.
Daniel Reid
Mobile editor
Follows phones, the software on them, and the slow business of making 2 platforms talk to each other.
