For the patient: harnessing the power of the sun

Batteries with solar cells are particularly worthwhile when hiking in sunlight, when you can place the device on your rucksack. However, it takes a while until the battery is fully charged: in a test by Stiftung Warentest, the cell phone was only about a quarter charged after around seven hours of charging.

In the car: New task for the cigarette lighter

In conjunction with a lead adapter, it is a reliable power supplier. It is important to pay attention to the quality of the adapter: The cable should be of high quality and not a cheap spiral.

Inexpensive and effective: "Powerbanks"

Depending on the size, you can charge your cell phone one to six times with the mobile additional batteries, connected via a USB cable. They then need to be recharged themselves. New devices store the energy required for charging for up to 28 days.

Steal from the big one: Tapping into the notebook

Even if the laptop is still fully charged, it can easily cope with the energy drain: a smartphone only requires ten watt hours of a notebook battery. These usually have 50 to 80 watt hours.

Free ride: Pedal away and store energy

If you are going on a longer bike tour, you can easily supply your smartphone with power via the dynamo using an additional device. The batteries can be attached to the bike frame either permanently or detachably. And then white textiles can be pedaled diligently at 60 degrees ...