Recently I stopped by the Tesla charging station at Fashion Island in Newport Beach, California. I wanted to add some juice to my battery for my trip home. I didn't NEED juice to make it home but it would have kept me from running it down into the yellow range. Fashion Island has one charger set up for the roadsters and one for the model S. The roadster charger was being used by an S with the adapter. I'm pretty sure the adapter had been lent to the owner from the store upstairs. The model S charger was open. I thought about disconnecting the model S and plugging the j-1772 into it, which would then have allowed me to use the roadster charger. I thought about all the possible ways this could go bad. The S still needed five hours of charge. I was afraid an alarm would go off if I unplugged it, is that possible? Then I also thought if his car was set to charge at a certain time, his charger wouldn't start charging when I plugged it in. I didn't want to leave the guy with less than a full battery since I figured if he needed that much charge, he was probably from out of town. I could have gone up to the Tesla store to see if they had an adapter, but for whatever reason, I didn't. Had I gone for the switch, I would have been gambling his car would charge. As a write this, it seems I did the right thing. But had his car, or any plug-in been fully charged, is an alarm going to go off when unplugging a locked car?