Power bank guides

Plain answers to the questions people ask about power banks, with the sources and the date we checked them.

All guides

• Can you take a power bank on a plane?
  Can you take a power bank on a plane? Yes, in hand luggage, up to 100 Wh without approval. How to work out Wh from mAh, and the rules for use on board.
• Magnetic charging explained
  What MagSafe is, how Qi and Qi2 wireless charging work, what 'magnetic ring compatible' means, and why a thick plain case weakens hold and charge.
• How many charges from a 20,000 mAh power bank?
  A 20,000 mAh power bank holds 74 Wh. After conversion losses, expect roughly 2.4 to 4.7 phone charges, by phone size. The arithmetic, step by step.
• How to charge a power bank
  How to recharge a power bank over USB-C, which charger to use, how long it takes, what the LED display tells you, and how to store it so it lasts.
• How to choose a power bank for your phone
  Capacity, wattage, wireless or wired, size against capacity, the 100 Wh airline limit and what to check on a listing before you buy a power bank.