Most commonly used in combination with the
Battery Bank. However the Double
Battery Bank includes an extra bill of higher
denomination set aside for emergency funds that is stored between the phone and its cover.
Friend 1: "Damn, I only put $10 in my
Battery Bank. I don't have enough cash to go with you guys."
Friend 2: "Don't forget about your Double
Battery Bank! I just saw you put $20 behind your
phone case yesterday!"