Most likely the battery is not being charged to the fullest potential or may be a lemon. The usb chargers just can't provide the amperage for the battery that it needs to get it to operate at peak performance. Like all e-cigs and vapes that take 18650 batteries and offer micro usb charging, we recommend charging with an external 18650 charger for improved performance and extended battery life. You can find these chargers for under $6 HERE or at any local E-cigarette store! If you believe your battery is bad, please fill out a service ticket on our website.