How do you choose a power bank with the right capacity?

A large 27,000mAh power bank has an actual 18,000mAh capacity, which allow you to charge multiple devices. That's useful if you want to charge your laptop, work smartphone, and private device. These large power banks always have multiple USB ports. That means you can charge your devices at the same time. If you only want to charge your smartphone, you can do that 6 to 8 times. So you can charge your device every day during a week-long camping trip. Or, share the power bank with your friends at a festival.

For laptops and power banks, you should choose a power bank with at least a 20,000mAh capacity. Tablet batteries have a capacity between 6000mAh (iPad Mini) and 11,000mAh (iPad Pro). The average is 8000mAh, which also goes for laptops. A 20,000mAh power bank actually has a 13,300mAh capacity, which allows you to charge your tablets and laptops at least 1 time. You can even charge small tablets 2 times. Exceptionally large laptops like the 15 and 16-inch MacBook Pro models require at least a 27,000mAh power bank.

A 10,000mAh power bank has an actual 6,660mAh capacity, which allows you to charge most new smartphones about 1.5 times. The size of a smartphone battery differs per device. While 2-year-old smartphones sometimes still have a 2000mAh battery, new devices have a 4000mAh battery. Make sure you check how large your battery is. Want to charge other devices in addition to your smartphone, such as earbuds, an e-reader, or a second smartphone? Choose a power bank with a capacity of at least 15,000mAh.

Want to know how often you can charge your smartphone with a 5000mAh power bank? Check how high the actual capacity is. It's 2/3 of 5000mAh, which is about 3330mAh. Almost all iPhones have a smaller battery than that, except for larger models like the 12 and 13 Pro Max. That means that you can fully charge your iPhone 1 time. Android smartphones like those from Samsung and OnePlus often have a 4000mAh or even 5000mAh battery or larger. You can't fully charge those devices.

Does your smartphone support fast charging? Choose a power bank with a fast charge protocol that your smartphone supports. All iPhones from the iPhone 8 support Power Delivery. This charges your smartphone back up to 55 to 60% within half an hour. New Android smartphones support Power Delivery and Quick Charge. This ensures that your battery is back up to 50% in half an hour. Do you have a Samsung S2/S22? Super Fast Charging is the fastest there is. With smartphones that don't have a fast charging protocol, it takes about 2 times longer.

The technical side of it is complicated, but the rule is simple. The actual capacity of a power bank is about 2/3 of the capacity indicated. The rest disappears due to voltage conversion or is lost during charging, especially as heat. This means that power banks with a 10,000 or 20,000mAh battery actually have a capacity of only 6660 or 13,330mAh. This rule only applies to high-quality power banks. Budget power banks from discounters are even less efficient, so they lose even more energy.