Well that really is something ... Who does not know, especially when it is time important, the phone / tablet or camera power goes out. Spare batteries may not always carry around with them and battery switch in wind and rain is also not recommended. So I bought this battery Power Bank, which is just slightly larger than a battery. A good idea and has fully convinced me right out of the. The external Aklku with its 3000mAh a cross-country skier, I got him never when using empty. We recommend!