A:Answer JBL Charge 4 has a built-in lithium-ion battery. The unit can be used even when it's plugged in, and it will not affect the battery. If ever the battery is full, lithium-ion has smart circuits, and the unit will automatically go into trickle charging. Unfortunately, we don't offer internal parts and battery replacements for our portable products. If you have more questions, please reach out to our Customer Support: https://www.jbl.com/support-contact.html