That's the problem with having a cheap ELM327 OBD dongle (or a rebranded one by people, like AA trying to get on the bandwagon) - they are just too dumb to understand 'ignition off' signal.
I had a similar experience to what Mike described above - flat battery after a few days of having a generic ELM327 plugged in. Replaced the battery (was going to anyway), and now only stick that thing in, when I want to fire up the Torque Pro app on my head unit.
And yet, a high quality OBD dongle can sit happily, permanently plugged in, without any issues: I've had my Garmin ecoRoute HD+ (an OBD bluetooth dongle for a Garmin satnav) for four years in the previous car, and for over three years in the current one - never a problem.
In fact, it is hidden inside the dash, and the only time it's off, is when the Y-splitter is unplugged from the main OBD port - this will shortly be rectified, with a custom harness I put together, so that the main port is free, and ecoRoute is plugged in [truly] permanently.
I had a similar experience to what Mike described above - flat battery after a few days of having a generic ELM327 plugged in. Replaced the battery (was going to anyway), and now only stick that thing in, when I want to fire up the Torque Pro app on my head unit.
And yet, a high quality OBD dongle can sit happily, permanently plugged in, without any issues: I've had my Garmin ecoRoute HD+ (an OBD bluetooth dongle for a Garmin satnav) for four years in the previous car, and for over three years in the current one - never a problem.
In fact, it is hidden inside the dash, and the only time it's off, is when the Y-splitter is unplugged from the main OBD port - this will shortly be rectified, with a custom harness I put together, so that the main port is free, and ecoRoute is plugged in [truly] permanently.