Power banks buying guide
A power bank's printed capacity is not what your phone receives, so a little arithmetic prevents disappointment.
- Expect roughly 60 to 70 percent of the printed mAh to reach your device once conversion losses are counted.
- A phone battery is around 4,000 to 5,000 mAh, so a 10,000 mAh bank gives about one and a half full charges.
- For laptops or tablets, look for USB-C Power Delivery and check the output watts match what your laptop asks for.
- Airlines generally allow banks up to 100 Wh in cabin baggage only; that is roughly 27,000 mAh at 3.7 V.
- Pass-through charging (charging the bank while it charges your phone) is convenient but not every model does it well.
Common mistake: Ignoring the input side: a large bank that charges at 10 W takes a full day to refill.