mkc4s

I also have Optima red top battery and do the same thing: plug my charger (non-porsche) into cigarette lighter, and the battery is being charged regardless whether the car is locked (with alarm) or not.

So there was some error in your charging: bad charger, bad battery, charger not fully plugged in the lighter, garage fuse went out, etc. You need to investigate.

97Targa

Good point. I have had my GFI (that the charger is plugged) into in the garage
trip more than once.