Reddit mentions of Electop USB 2.0 A Female to Dual USB Male Jack Y Splitter Charger Cable Product Name

Or splitting one keyboard across 2 computers - one with online client +FL and the other with offline client without FL. Play normally reading on offline client, submit over online client +++profit.

That's what most taiko FL players do anyways

Sorry for delayed response. I know there was a similar request, but I was mid-move when it came through.

The deets:

Ordered this: https://www.amazon.com/gp/aw/d/B01ALLWDFW/

One USB A is data and power, another is power only. This alone worked well enough...

I wanted to feel more responsible in charging the phone, so I used transparent tape to cover only the outside pins of the data+power USB A plug.

Then the data cord goes into the AA port and the power cord goes into the good charger. I don't get turbo charging, but I get topped up and I stay there - with Navigation, GPS, and Google Play Music running nonstop.

I just plug into the cord and I'm off and running. Added some Tasker stuff to make things slightly more automagical. But that's the gist.

Loving it. Just did a six hours drive with all of that and finished with 100% (I was there almost all of the drive). In fact, this set up is what I used when I drove over 1k miles for the move. It's proven, IMO.

Yep, adapters like this split out data and charging to separate USB male connections. As far as fast charging you might find difficulty finding one that supports as those features typically require some connection on the data pins.

You could also use a USB hub, possibly, by plugging the host port into the stereo. That's more of a question-mark though as I don't know if the communication protocol will work with with a hub chip in the middle.

Something like this or this.

Same idea. The advantage there over a powered USB hub is portability. Bring a battery pack and power the thing outdoors or in a remote space.