Computer power bank is an external battery charger with 12V 16V 19V 24V output for charging laptops. Everytime when we say power bank, we are thinking about the power banks for smart phones, MP3 and other 5V electrical devices. Normally the battery of cell phone power bank is from 1000mah to 10000mah. Because the battery capacity of cell phones are around 1500-3000mah. So small battery power banks are enough for charging smart phones. For charging cell phones, we like power banks small, light weight and slim. But for laptops, their battery capacity inside is large, so laptop/computer power banks are normally with high capacity battery inside. For different computers, we need different power adapters for charging. Pls see below picture.