They are built it, but replaceable. It's not a task I would suggest undertaking though. As a friendly suggestion I would recommend something like a KBOX Mini starter kit. You can simply buy replacement 18650 batteries and have them charged and ready to go. It has a magnetic door and it's extremely easy to pop in a fresh battery to keep vaping. Pricing ranges from 54-85 depending on where you shop. I know this does not necessarily fix your problem, but it offers a nice replacement with minimal hassle.