Is leaving the dongle in and on harmful?
Our strong advice is not to leave the dongle active in the car while you’re away. In essence, it is a not-secure direct access device to the main CANbus of the car, with a default Bluetooth password. I have been able to wake up all the ECU’s from a sleeping Zoe using just the dongle. Things like opening doors are probably pretty hard to do but I wouldn’t consider it wise to believe it is impossible. That is one more reason we like the Konnwei – Maxiscans: they have this little on/off button on the top (unfortunately, they do not seem to go to sleep after half an hour of CANbus silence as the documentation suggests, but alas). At least it is easy to switch it off.
Another side of the question is power usage. I am bringing this up as my Zoe was completely and utterly dead this morning with a flat 12 volt battery. So, I decided to check how power hungry my dongle is: less than 1 mA when off, 40 mA when on with a sleeping CANbus, so that should drain the battery of not more than 1 Ah per day and should not be an issue.
Bottom line: be smart and switch it off. If not, and she’s still there where you left her, no harm done.
PS: It was really odd as the car was connected to the charger (had not charged for one reason or another), but the traction battery was still at least half full. My charging logging email from Renault suggested that she had her last charge in the night from December 30th to 31st. That could be right, as there was virtually no driving last week but last night definitely is strange. I have a suspicion about what happened but before I am sharing that I need to get rid of the error and ensure the 12 volt battery is not a dud.
Update: I had her up and running again after charging the 12 volt battery enough (a few hours on 3A) to wake her up and start charging. Never ever do this with the car connected. Remove the minus lead and, as the car can decide to try to charge the battery even with the contact off, make sure the lead is isolated. My suspicion is that the charger plug was not seated correctly and it tried locking it for a couple of hours with most of the ECU’s awakened by the dashboard computer. After charging there was a message to check the electrical system, but that went away by itself.