CANBUS adapter cable and OBD BT install question

[Alset2]

I have read and read but thought I would just ask. I have ordered adapter cables and OBDlink so I can get Scan MY Tesla app working.

Do you have to power down to hook up the adapter cable and OBD reader ?

I have read and seen videos of people plugging it in with and with out powering off.

I have an extensive automotive repair background and to be honest, I would not have even consider the need to power down to hook up a diagnostic reader... until I came across mention of it in all my reading.

I will not use it for real time telemetry, I will just used it to check on things once in while (and I like data!!)
I also ordered a cable for my wifes M3, is it ok to just leave the adapter cable hooked up with out the OBD reader ?

I feel a little silly asking these questions (if you knew my background you would laugh with me) but I simply dont want to mess something up becasue I THINK I am soooo smart about cars...lol
...and these are not JUST cars if you know hat I am saying

Thank in advanced

 

[webfootguy]

It is a good idea, but I did install it in my M3 and did not power down. I was just careful with the connectors and make sure not so short anything out and the install went fine. It works well with the app BTW. I leave my OBD reader connected all the time when I drive daily but now that I am only driving a few times a week, I have unplugged it as to not put unnecessary strain on the 12v battery. I believe it will charge it up even when parked, but I don't want to risk it.