Batteries – they all run out of power eventually. And that sucks, especially when there's no power outlet around, yet you desperately need to use your smartphone or tablet, be it for work or something just as urgent. Well, that's why we have portable battery packs. For those not familiar, they are like a tank of battery power that you charge and use in emergencies by plugging in your gadget in the accessory's USB port. They come in many shapes and sizes, but if you demand having the largest one possible, look no further than the list below. Ladies and gents, we give you the largest portable battery packs for smartphones and tablets. Check them out!