Hi!
I think there is something wrong with the battery of the speaker, you should replace it.
[guide|41670|This] guide will help you and [https://www.google.ro/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=0ahUKEwiRre6n1_7VAhWqNJoKHdUoAsgQFghQMAo&url=http%3A%2F%2Fwww.ebay.com%2Fitm%2F3-7V-6000mAh-Speaker-Battery-Fits-JBL-Charge-Replaces-AEC982999-2P-%2F232031856540&usg=AFQjCNEfwZh5VTAIv7IP4Kk5u6vJzvDw3Q|here] is where you will find your replacement battery.