The times where cell phone batteries lasted for several days are now gone. There´s now this black and white external battery, also known as a power bank, which suits as a portable companion for traveling to charge cell phones, tablets etc. at any time. To recharge itself, you have to connect it to an USB port, like a phone charger or a PC. With a loaded power bank e.g the iphone can be recharged up to 5 times and an iPad for instance up to 2 times. You can connect two devices at one go.