BERLIN: Power banks are very handy items to have when your phone or other devices need a charge, but there's one thing you need to be ready for: the sudden hazard that comes when you drop them.

If a short circuit happens within the battery cells, typically from falling onto a hard surface, the power bank can overheat or catch fire, warns the TÜV safety inspection body in Germany.

Damaged devices can be identified by inflated or deformed housings or where exterior parts are melted or discoloured. Power banks in this condition should be disposed of immediately and in the proper location such as a recycling centre.

If you’re travelling by air, power banks may only be carried in hand luggage. The fear is that, if stored in checked luggage, it could catch fire in the luggage hold.

It’s also rarely permitted to charge one on a plane. The number and capacity of power banks permitted on board varies from airline to airline, so it’s best to check the airline's website beforehand.

If you’re buying a power bank, there are a few points to pay attention to. The output voltage of the bank shold match the operating voltage of the devices that you want to charge using it. Most power banks have 5V, which is enough for smartphones but not laptops, which often need 12V or more.

According to the TÜV safety experts, modern power banks often also offer an intelligent charging mode that adapts to the charging processes of different devices. It's likely to cost a little extra, but you may get more use out of a power bank that can charge both your phone and your laptop.

It’s also worth getting one that allows pass-through charging so that you can charge devices from the power bank while it’s being charged itself. And you may want to avoid a small-battery power bank. A power bank with a 5,000 mAh battery will be light, slim and compact, but won't get you much more than one smartphone charge.

 - dpa