A power bank is the easiest accessory to get wrong — inflated capacity figures, slow ports and dodgy batteries are everywhere. Here's how to read the specs and buy the right one, once.
Start with real capacity (mAh)
The headline mAh number is the battery's capacity, but your phone gets less than that after the voltage step-up. A 20,000 mAh bank realistically delivers roughly 4 full charges to a typical 5,000 mAh phone. Match the capacity to your need: 5,000 mAh for a pocket backup, 10,000 mAh for daily carry, 20,000+ mAh for travel.
- 5,000 mAh — emergency top-ups, credit-card size
- 10,000 mAh — daily carry, two phone charges
- 20,000 mAh — multi-day trips, still fly-safe
- 30,000 mAh — laptop + everything, definitely fly-safe
Airline rule
Most airlines allow power banks up to 100Wh in carry-on. A 20,000 mAh bank is ~74Wh, a 30,000 mAh is ~111Wh — check your airline before buying the big one.
Check the port, not just the watts
USB-C Power Delivery is the standard you want for fast, modern charging. Look for 18W+ USB-C output, and USB-C in so the bank recharges with the same cable your phone uses.
- USB-C PD 20W+ — fast phone charging
- 65W USB-C PD — laptop charging from a bank
- USB-C in/out — one cable for everything
- Pass-through — charge the bank and your phone at once
The best power bank is the one you actually carry. Don't buy 30,000 mAh if you won't carry it.