This powerbank will not let you down. Conventional powerbanks for recharging smartphones and tablets are usually empty just when they are needed. The Voltcraft SL-240 Powerbank has built-in solar cells that do not allow the powerbank to self-discharge - as long as the powerbank is stored in a suitable place (e.g. on the windowsill). In sunlight, the powerbank charges itself. Free of charge and completely self-sufficient. A faster way is to use the integrated USB port. When the powerbank is charging, an integrated LED lights up green. As soon as the Powerbank is fully charged, the LED lights up blue. The powerbank has two USB outputs (1x USB-A and 1x USB-C). This allows you to charge up to two devices at the same time. Have light in the dark at all times thanks to the integrated flashlight and SOS function. In emergencies, you can draw attention to yourself with sufficiently bright light.