The battery size of 550mAh is significantly smaller than the Box 4000 Puffs series 1500mAh. This is because it’s a rechargeable device. To make full use of its 16ml juice oil, a non rechargeable 1800mAh battery would be needed and it won’t fit in any handhold device so far. That’s why rechargeable design is a better solution for the 6000 puffs.