How to Choose a Power Bank: Capacity, Output and Flight Rules
A power bank is a portable battery for charging phones and other gadgets away from an outlet. The label numbers can be confusing, so here is how to read them.
Best for: Travel, commuting and long days away from outlets.
Skip if: You only need a small top-up and want something pocket-sized.
Check first: Output wattage, port types, weight, and airline battery limits.
Capacity: mAh and watt-hours
Capacity is usually printed in mAh. To estimate energy in watt-hours, multiply mAh by the battery voltage (often about 3.7 V) and divide by 1000. A 20,000 mAh pack works out to roughly 74 Wh. Usable capacity is lower than the label because of conversion losses, so expect a phone to get roughly two to four charges, depending on the phone.
Output and ports
Check the output in watts and the port types. A phone needs far less power than a laptop. If you want to charge a laptop, look for a model that lists a high enough USB-C output.
Flying with one
Airlines generally require power banks in carry-on bags, not checked luggage. Many airlines limit spare batteries to 100 Wh without special approval. Check your airline's current rules and the Wh figure on the label.
Our analysis
Bigger is not always better. A larger pack is heavier and takes longer to recharge itself. Match capacity to how long you are away from an outlet, buy from a reputable brand, and stop using any pack that is swollen or damaged.
Where to find it
20000mAh Power Bank
Prices and availability are set by Amazon and can change. Check the live price on Amazon before you buy. This button opens search results, so pick the listing that matches the checks above.
Editorial note: VryzoxDrop has not tested these products hands-on. This guide is based on the product listing and general knowledge of the category. Specifications and listings change, so check the details on Amazon before you buy.