Is OBDII Bluetooth device draining battery?

Hi, thanks for reading this post.

Can anyone tell me if the on-board diagnostics port on my Audi S3 8v will power a device when the ignition is off and all of the doors are locked?

I have been getting a warning when I start the vehicle telling me my battery is low and will be charged while I am driving.

I made another post on this forum about this and it has been confirmed that none of the cigarette lighters in the vehicle provide power to my dash cams or to my Snooper when the ignition is off and the vehicle is locked.

Today I remembered about the Bluetooth dongle that I have permanently connected to my OBDII port. When I turned the ignition off and locked the vehicle the red light on the Bluetooth adaptor was still on. This made me think my Bluetooth device might be a drawing current from the battery permanently when the vehicle is locked.

You can buy Bluetooth OBDII adaptors with an on-off switch and this might be the reason why.

I have disconnected my current Bluetooth dongle to see how it goes over the next few weeks but it would be great if someone could confirm this might be the cause of my battery warning.

I fitted the Bluetooth dongle in January and of course we had some quite bad weather january-february and March so I put the battery warning down to the cold weather when it might actually be my Bluetooth dongle.

Thanks for reading any advice greatly appreciated.

Hi, thanks for the reply.

My car is 3 years old this month.

I have just read another post where someone said they were going on holiday for a week, parked their car at the airport then remembered they had left their OBD2 Bluetooth dongle connected.

Someone replied to say the Bluetooth dongle usually doesn't try to communicate unless the car is running. These Bluetooth devices usually only have one tiny LED that stays lit (like mine does).

Apparently when the ignition is off there is a current draw, but it is very small. The person said they leave their Bluetooth dongle connected permanently. They drive several times a week and it starts fine every time.

This coronavirus during the past few months means 5+ days have gone by when I have not driven the vehicle. Whilst I do get the low battery warning, it starts first time every time.

So I think the answer is yes, the OBD port is powering my Bluetooth dongle 24-hours a day, but the drain on my battery is small.

On the other hand, the battery drain is big enough for my car to recognise something is going on and to tell me the battery is low (yet when I connect a cheap battery charger from Argos the indicators show the battery is 100% charged)?

I have spent a lot of time setting up my Android screen to work with my Torque application so I will buy a new Bluetooth dongle that has an on/off switch. At least I can then switch it on when I want to use my screens and off again without having to keep forcibly unplugging it from the port.

Thanks again for reading.