JBL Battery 400 - an Easy-to-Replace Spare Battery That's Compatible with The JBL PartyBox Stage 320 and Xtreme 4 Portable Speaker (Speaker Sold Separately)Compatible with JBL PartyBox Stage 320 and Xtreme 4: JBL Battery 400 is only compatible with the JBL PartyBox Stage 320 and JBL Xtreme 4 wireless Bluetooth speaker. Other JBL PartyBoxes and JBL portables have different battery requirements. Keep the party going twice as long by having a spare JBL Battery 400 on hand: Just swap out the battery in the back of your JBL PartyBox Stage 320. Each battery has up to 18 hours of playtime, which means you could