If your JBL doesn't charge anymore, it is either the battery, or maybe this problem:
I show how to fix a bad solder joint on the charger/headphone jack on a JBL head phone.
Confused? No? Just watch.
First you have to take the 2.5 Jack Board out, then re-solder the contact points of the headphone and charger jack.
Put everything back together, and you are good to go.
I hope this video helps!
Click on the i in the upper right corner to find my video where i explain how to take the headphones apart.
Here the JBL E40BT Teardown video: • JBL E40BT Teardown