First of all I am new to this forum and looking for some insight for a project.
I have a little blue tooth receiver coming in the mail that I'll use in my car and at home but as I'm waiting for it I want to get the issue of powering it out of the way. I have a switched DC jack and a Li-Pol battery and would like to ask if there's a circuit I could build to disconnect and charge the battery while the module is powered by DC?

 

So you don't want to boost 3.7V up to 12V, but to use something (12V?) to charge the battery?

 

The bluetooth receiver runs on 3.7 but I have a buck regulator to step the 12v DC down to 3.7 so it can run on DC as well.

 

So it is a charger circuit for a single LiPo cell that you want?
What do you want to use as the power for the charger?

 

So it is a charger circuit for a single LiPo cell that you want?
What do you want to use as the power for the charger?

Pretty much, a circuit that would disconnect the battery when using the DC input and I guess I would need a separate port for charging? Or could the DC charge and power the module at the same time?

 

The DC input would be 3.7V to power the bluetooth and you would have to boost that up before you could use it to charge the battery. A LiPo charger could run from the 12V.

 

The DC input would be 3.7V to power the bluetooth and you would have to boost that up before you could use it to charge the battery. A LiPo charger could run from the 12V.

Could I have a SPDT switch to toggle between charging and powering the Bluetooth? I could just the the power before the buck regulator to get 12v so I wouldn't have to step it up.