Wicked Chili 2100mA / 10.5 W Dual USB Car Adapter Universal for Sony, Nokia, LG, HTC, Motorola, Wiko, Huawei, BlackBerry, Samsung, TomTom, mobile phone, smartphone, tablet and Navi (V3.0, 12V / 24V, 2x USB) (Accessories)
After I already had negative experiences with other adapters, was able to convince me of this 12 / 24V adapter completely.
It was used until now only with a cell phone (Samsung Galaxy S3). Although Spotify ran with audio streaming parallel to the navigation and the phone glowed merrily to himself, the battery is reliably charged!