C5040 is made by Li-Polymer battery. 1 USB in and 1USB out. Output 1.0A. Not only smart phone, but iPad is ok. It is slim. It is only 112g. You can carry it anywhere. and put it in your backage, You will not feel heavy. When you have to take a call, your cellphone runs out of power. You need to recharge yoru battery. Therefore, you need a power bank.