Can't believe they were all hooked up to charging stations on the boat from Germany, so you should be OK. Just make sure the 12v battery has a full charge before the car goes on the transporter. 
Does your ED have the 2016 BMS software update? More on this in this thread:I've heard both ways. It only charges when the key is on, and it charges from the traction battery as needed. Could be a difference in the firmware. But from my experience with my 2016, the 12 volt drained and the traction was still 100%, which leads me to think it is only when the key is on. I topped off my traction battery when I parked it Dec 14th. My 12 volt went to zero. 10 days later I jumped the car from my ICE. Just checked today still 100% in the traction. I'm sure the cars sat on lots for way more than 30 days without maintenance. I wouldn't cut my trip short.
Lithium ion batteries do not self-discharge - so the car should stay at 100 percent. Since you car is a 453 and is not prone to that BMS software bug that causes the 451 ED battery to totally discharge itself when the 12 volt battery goes flat, you should be fine.When I left it was charged at 100% and I unplugged it. Should I ask a relative to go and plug it back in? Will that protect the Drive battery?
Thank you. I bought this 2017 Electric Smart only a few months ago, and I love it. It drives like a sports car and can do a u-turn in my driveway. I'd hate for something to go wrong.Lithium ion batteries do not self-discharge - so the car should stay at 100 percent. Since you car is a 453 and is not prone to that BMS software bug that causes the 451 ED battery to totally discharge itself when the 12 volt battery goes flat, you should be fine.
Also on the 451's, keeping the car plugged in for charging when the HV battery is full does not charge the 12V battery. If fact, the charging plug does even get energized unless the car sends a "HV battery needs charging" signal.
To be sure the 12V battery stays charged, the keyswitch needs to be turned on for a few minutes every 2 weeks or so.
Same here bought a 2017 in July. It's still under warranty, so if the battery fails... anyways, I believe the 12v battery issue is more with the 451 ED's, but the 453 ED's and EQ's like ours not so much.I bought this 2017 Electric Smart only a few months ago, and I love it. It drives like a sports car and can do a u-turn in my driveway