@Dgonik what you are trying could be considered a hack.

The device is not intended to be used as you want. If you plug it in, it will start charging, AFAIK.

I know a hackish solution:
- go to a x terminal console, and type
- sudo gainroot
- stop bme

That way, you will be stopping the glorious Battery Management Entity, so then you could plug in your phone to the pc and it will not start charging.

I'm not sure about the secondary effects. BME is an important part of the phone.

remember to turn it on manually later.