Our JBL Flip 6 emits an audible sound notification (a distinct descending chime or tone) when its battery is running low. In addition to the sound, the LED indicator near the charging port will start flashing a pulsing red light to visually warn you that it's time to plug it in before it powers down. On the other hand, it has a playtime of up to 12 hours which may be reduced when you turn up the volume, much like a phone battery when you brighten the screen. The same goes for source material. Music with more bass will also reduce playtime. It is possible that the battery is working correctly but depletes more quickly when the volume is very loud and/or the bass has been boosted. Battery playtime also decreases as the battery ages and all batteries, over time, will slowly wear down. Please charge the speaker to 100% and then listen to music without any bass boosted, and at a low volume. If the battery lasts close to the published up-to playtime, the battery is working fine. However, if you get less than 90% of the published spec, please contact our customer support for further assistance.