Unfortunately, it needs the batteries. A little tip: it quickly displays 1 out of 3 lines. But depending on use, it will last easily half a year.

Thanks for the answer. It's good if it lasts a long time. - but for me it is very illogical why it has to be battery operated in a car where it has electricity?! strange

Only the control unit, but it is very economical, battery lasts a long time