Mine is plugged in full time. But what I did is I wired a switch so that I can switch the power ON/OFF. But for the few occasions I have forgotten to switch off overnight after use I havent noticed any battery drain. So I dont think car battery is an issue.

The reasons why I wired a switch are that:

1. I feared that when the Obd adapter is powered all the time that might cause damage to the device in the long run. I really am not sure about any possible damage but I figured out that I would rather be safe than sorry.

2. when Obd tool is powered any other person can pair the Obd scan tool with their phone or comp. I am not sure what else you can do after pairing the device but my gut feeling is that it would be unsafe especially in the hands of a clever hacker.....

3. My obd scan tool (OBDKey) emits a bluish LED light as long as its powered on. The light can be annoying inside the car especially when one is not using the device.

By the way the Kiwi adapter has its own ON/OFF switch.....

I noticed on my vehicle that if I left it in, the remote door locks did not work all the time, took a bit before it unlocks or locks and had to be right next to vehicle. Have it removed, and the locks work like normal again. Of course it is a cheap ELM327.

I leave my cheap eBay one plugged in all the time and haven't noticed any problems.

Good info, thanks guys. I got the cheap ebay one, too (XiTech). It has one red LED on when it's plugged in which surely isn't much of a drain.

I'll probably leave it hooked in most of the time, and yank it out if I think of it, or am otherwise so inclined.

Since I will have o take half of the interior apart to plug it in or out, I will try to rely on the powersave functionality... Won't dismantle the car everytime....

I'm running a Kiwi Bluetooth and I leave it plugged in and on w/o any issues.

Probably depends on the health of the battery... When I've forgotten to unplug mine (ELM327 from eBay) overnight, it completely drains the battery, and I've had to jump start or leave the car on a trickle charger a few times.

My car (and hence battery) are both about three and a half years old, and it's had some fairly long (up to 7 weeks) periods of being parked up while we've been on holiday, so that's probably not done it any favours.

The scantool.net has a powersaving mode that Torque supports if you turn it on in the settings (though you will need to make sure the adapter firmware is on the latest version)

OBDKey seems to be alright for a couple of days, as do *some* of the ELM327 adapters, though if I leave it more than a week without charging the battery then it's jump-start time.

There are security implications for leaving the adapter in, however, the ECU shuts down in most vehicles after 30seconds of the ignition being turned off (so communication with the ECU should then not be possible). This may not be true for all vehicles however (I am not an expert :-)), so you would have to check.

Ian

My cheap dealXtreme one is plugged in all the time, never noticed my battery voltage getting low at all.
My OBD2 connection shuts off 30 or so seconds after I turn the key off. Now there may be a way to force it to connect but if there is I don't know what it is.

My cheap unit (from dealextreme as well) is always connected. I even forgot it connected over a long holiday (4 days) but still had no problem. A red LED stays on even after the vehicle is off, but seems to be to low to drain the battery.

Anybody found the way to unlock the door (when you locked your key in) via Android Torque app?
Perhaps there is a plugin?