Blinking Red light while charging

Check JBLs website to interpret lights. Flashing red may indicate low battery or if used regularly, may be a worn out battery. Rechargeable batteries won't last forever and average life span may be a few years with regular use, hundreds of recharges. Review the Guides section on disassembly if you're determined to make repairs, assuming a worn out battery. Once disassembled, you'll see the battery pack and labeling to shop for a replacement. Soldering skills needed to desolder and solder new battery wires. A multimeter can help measure voltages; charging adapter, original battery, etc. If you disassemble yours, you can make a substitute battery pack from AAA, AA, whatever, as long as voltage matches the original battery pack labeling. A little higher is OK. This way, a substitute battery pack should power up and restore headphone function while shopping for a replacement rechargeable pack, available online in any size to suit your needs.