Visited yesterday on foot but didn't see the chargers.
I remember coming here back in June 2020 looking for the chargers but didn't find them.
There are actually signs pointing to the underground parking including EV signs, I don't remember whether those signs were there the last time I came by, maybe I didn't go far enough down the road when coming counter-clockwise. If you drive clockwise around the buildings, there are actually 2 different signs pointing to the parking.
There's an entrance to an underground parking and it doesn't seem like there's any door or gate. The sign at the top of the ramp has a parking meter sign. There are also opening hours written above the entrance, 07h-23h.
I wanted to go in on foot but was not able to find any entrance. I assume you have to enter one of the Burgerheim buildings and then use the interior staircase. I'll go back with the car in the future.