My car has aux and bluetooth - but only for phone calls. WEIRD :( So I decided to add another bluetooth for listening music and podcasts.
With little research I found that bluetooth receivers and headphones need "aptX" for high guality sound. The cheapest I found on Aliexpress "Link-485".
There is a little trick. BT receiver has battery inside and for pairing you need to press button for 5 sec. But I want this to be automatically, when I start a car.
The original instructions I found here http://goo.gl/q45mli
Step 1: Soldering
I needed 2 capacitors.
One small for switch and one "big" to replace battery. If I would leave battery inside, BT receiver would not shut down until battery would be empty. With capacitor it shuts down immediately with the car.
For replace battery I use capacitor 10V 3300µF but it was tested also with 10V 2200µF.
For switch is enough 0,47F.
Be careful with polarity - watch my pictures!
Step 2: Power Supply
I use Lithium Charger Step down 5A 5V-32V to 0.8V-30V Power Supply Module LED Drive 5A
and cable with fuse "add-a-circuit".
Step 3: Installation Into Car
You can see I had problems with too big capacitor. I use hot glue gun and fill gap with glue:)
I also glued receiver with the same glue under steering wheel.
It is "invisible" but still enough close if I need buttons.