You can park in a small car park on the Route des Crêtes (before the descent to the Steinwasen farmhouse inn).
(S/E) From the car park, take the Red Rectangle-White Rectangle-Red Rectangle marked trail (a variant of the GT5) which heads north towards the Rothenbachkopf. After a few hundred metres, it reaches a junction.
(1) Turn right towards the summit of the Batteriekopf. Once at the summit, enjoy the panoramic views.
(2) Continue straight on, heading north towards the Rothenbachkopf. A few dozen metres from the summit, veer right to reach it.
(3) At the summit, take the small path on the right leading downhill, marked with a Red Disc. The path passes through beautiful forests and leads to the Steinwasen farmhouse inn.
(4) At the farm inn, take the uphill path marked with a Yellow Triangle. A little further on, leave the marked path and take the track on the right. At the very top, you will find the small car park where you started (S/E).