Jabra BT500 won't power up
If you can try a different charger, try that. try charging with USB cable if not. Try your charger on another headset if you can. I think the charger is the problem.
If no change every way, here is the link to the user manual if you need it;
Page 7 has the toll-free tech helpline which is probably worth a check in case they have any ideas before opening it up.
If still no luck, and you want to open it up, first thing to look for is the battery. check any connectors are on properly. try charging for a while and see if battery gets warm/hot/no change. See if there are any technical specifications or part numbers written on the battery and I can get more info to see if it can be checked and if it is worth replacing. If you have any trouble identifying the battery, try posting back a photo of the inside and we will see what we can do.
Hope this helps :)