Dear Janne,
Thanks for contacting us.
The passthrough you are interested in can not work with AC-USB adapters to charge in a socket because we tested it for many times. Maybe the output of AC-USB adapter is not identical with the input of the passthrough.
But we do have one passthrough that might suit your need-V.V. 650mAh passthrough. It has three volts and very good quality. It also contains a battery inside, so it is not merely passthrough but a combined device of battery and passthrough. Besides, the USB cord is detachable and retractable which is very convenient. Here is the link for you. Hope you like. For detailed info, please refer to this page.
http://www.healthcabin.net/index.php...oducts_id=7879
Any other questions, please feel free to let us know.
Best regards
Healthcabin