How to choose a good power bank

• Real usable capacity is roughly 60-70% of the printed mAh because of conversion loss.
• 10,000mAh charges most phones about 2 times; 20,000mAh about 4 times.
• Choose fast charging (18W or more) if your phone supports it.
• Check for multiple ports and the right cable type (Type-C is common).
• Very cheap power banks with huge claims are often fake.

Do not leave it in a hot car and replace it if it swells.