How to charge a power bank

Plug a USB-C cable into the power bank’s USB-C port and into a USB-C wall charger, and wait until the display reads 100. How long that takes depends on the charger.

Published 30 October 2026 by ONDO.

Step by step

Use the USB-C port on the power bank; on the ONDO 20K it is both the input and an output.
Connect it to a USB-C wall charger with a cable in good condition.
Watch the LED display: it shows the charge in per cent and climbs as the power bank fills.
Unplug it when the display reads 100.

Which charger to use

The ONDO 20K accepts up to 22.5 W over USB-C, as the manufacturer states. A wall charger that can deliver that much recharges it fastest; a smaller charger, or a laptop port, works too, only more slowly. The charger is not included in the box. We will publish which chargers reach the full input once we have tested them.

How long it takes

It depends on the charger and on how empty the power bank is. A 20,000 mAh power bank holds 74 Wh, so even at the full 22.5 W it needs more than three hours in theory, and losses add to that. We publish our measured recharge time for the ONDO 20K after testing, with the charger we used.

Why the display matters

A display in per cent tells you exactly how much is left, so you do not set off with a power bank you thought was full. It also shows you when a charger is too weak: if the number climbs very slowly, try a stronger charger or another cable.

Looking after it

Charge it while you are awake and nearby, not overnight and not while you are out.
Never charge it under a pillow, in bed or under a cover.
Keep it away from heat: radiators, direct sun, a hot car.
For storage over weeks, leave it part-charged, around half to three-quarters full, and top it up every few months.
Stop using it if it swells, leaks, cracks or gets very hot, and do not charge it.

The charging rules follow the published advice of Scottish Fire and Rescue Service and West Yorkshire Fire and Rescue Service, read 30 October 2026. The safety page covers the EU rules and documents.

Before a flight

You do not need it full to fly. EASA prefers power banks to travel part-charged; the power banks on planes guide has the rules.