Visited yesterday without charging.
The chargers are in level U2.
The parking has 2 entrances, both can be used to reach the chargers. There are "Ladestation" signs , though I did miss them on my first drive around U1.
If you enter from the North entrance, you end up in U1, drive along the first row and at the end there's the ramp down to U2 and the exit. There's an EV sign pointing down and at the bottom of the ramp you will see the chargers.
If you enter from the West entrance that has the "short term parking" sign, you drive down the ramp and there's a fork for the short term and long term parking. I didn't enter there and only looked at the entrance from inside so I'm not sure if there's an EV sign at the fork. You turn left towards long term parking, through the ticket gate and end up in U2. Then you drive around the floor, there are EV signs showing to stay on U2 and not take the ramp to U1. When you approach the exit you see the chargers.
There's a floor plan posted in multiple corridors but it doesn't show the chargers. Based on the floor plan and the signage outside the parking, it seems like the short term parking might have been just a parking meter in the past, but now it has gates, and its prices are posted next to the long term prices on every payment machine. The price is different for day and night.
The website for the parking doesn't really mention the chargers, except in the new section where there's a paragraph about those "new" chargers, but the information doesn't have a date https://www.aare-parking.ch/bahnhof-parking/news
There are also 3 AC chargers right before the exit for the electric Mobility cars.