As far as I know bluetooth is a radio frequency based communication protocol. It is designed for low power and short distance communication.
There are microwave wirless battery charging techiques, but how can you use a protocol based wireless data transfer to charge a battery? Bluetooth uses frequency hoped spread spectrum, I think. Inorder to receive such signals, the receiving device (your charger) should be running using an already charged battery!!
Don’t worry, these are my genuine doubts, please correct me if I’m wrong.