High charging, but new interior harness?

well i pulled the battery over the winter and kept it topped up in my living room.
I've driven about 200km since i pulled it out (this lockdown had made it semi-illegal to go for cruises here in quebec). Now every single time i take the volt reading is within a few minutes of starting it. do they charge at 15 volts, then after driving for 30 minutes or so come back down to a regular number? I didn't even think about that. This is my first classic car so I am still very much learning.