[Q] Powered USB OTG topic

I've been looking all over the net. I need a microUSB OTG cable that will charge at the same time. I've seen some half solutions. but nothing really doable.has anyone in XDA found a solution.
i would like this as i have mounted a tab3 in my cars dash and need a DAC to clean up the sound but can't use one while charging. Even if anyone else has any solution. I would be grateful,
thanks
Chris.