I had the same problem on my JBL flip 4..I do not know what blue tooth speaker you have but I will share this. When I use a fast charger or any other charger except for the one that specifically came with the charger, mine does the exact thing as yours. My first suggestion if you do not have the plug end ( as most come with some form of a USB plug) research the specific amps or power that your speaker needs. This is actually crucial if you value the longevity of your battery. Another place to look is your cable. I've bought many after market cables and I can promise you ( with out getting all tech specs) your cable does matter. Also if you plug your speaker in when it's at a low battery it will shut its self off thinking that the current is insufficient to both charge and at the same time play your speaker……..I hope this helps :)