Visited on January 6 without charging.
The charger is outside the building and is accessible 24/7.
The signage indicates that the few parking spots outside are subject to the same parking meter as those inside, but as all meters are inside there is no way to pay when the store is closed. The tariffs on the parking meter repeat the opening hours, so it should be alright to not pay when the store is closed. It starts at 60ct for 30min, no free period. It says max 3h (5CHF).