Power banks: what the number on the box means
Published
A 20,000 mAh power bank won’t give your phone 20,000 mAh. Some of the energy is lost along the way. For a family, our pick is the 20,000 mAh size anyway, because it leaves plenty to spare.
What the number means
mAh is how much charge the battery inside holds. A phone charges at a higher voltage than the cells inside a power bank, so the power bank has to convert it, and its circuits lose a little more on the way. Less reaches the phone than the box suggests. In Anker’s own example, a 10,000 mAh power bank delivers about 6,000 mAh.
How much you need
This is our suggestion:
- 1 or 2 people: a 10,000 mAh one, like the Anker 10,000 mAh (Ad).
- A family: a 20,000 mAh one, like the Anker Zolo 20,000 mAh (Ad).
In the government’s 2026 survey, 54% of adults had one. If yours is in a drawer somewhere, it counts.
Making it last
- Turn on your phone’s low power mode.
- Close apps you don’t need.
- Use the phone for calls and messages, and an FM radio for the news. Here’s why the checklist says FM radio.
Keeping it ready
Charge it when the clocks change, and again after you use it. It’s one of the steps on the clocks-change kit check.
Safety
Buy a known brand: it’s a lithium battery. Charge it on a hard surface, like a kitchen worktop, not on a bed or a sofa. That’s the advice from Essex County Fire and Rescue.
Both of our picks are on the light and power kit page.