JBL Battery 400 (JBLBATTERY400) is a replaceable battery designed for JBL PartyBox Stage 320 and JBL Xtreme 4 speakers. Each battery provides up to 18 hours of playtime, allowing up to 36 hours with a spare battery. A 10-minute fast charge gives an additional 2 hours of playback. Battery status can be monitored via the JBL PartyBox app, and replacement is quick and easy.