How much power does a Bluetooth OBD2 drain when ignition is off?

.00654 milliamps. You should be safe! Mine stays plugged in all the time, but I drive it almost everyday too. It doesn't try to communicate unless the car is running. And there's only one tiny led that stays lit. Enjoy your trip, don't sweat it.

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I have one too and I left it on over a long weekend when the temperature dropped to -35 here. It did not drain my battery enough to give me any problem starting on the following Monday.

sol

Last time I parked my car and left obd2 plugged in for about 4-5 days the battery was drained by the 5th day I went to start the car, Hope yours is not the case.

PRM502STREET said:

.00654 milliamps. You should be safe! Mine stays plugged in all the time, but I drive it almost everyday too. It doesn't try to communicate unless the car is running. And there's only one tiny led that stays lit. Enjoy your trip, don't sweat it.

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janitz said:

I have one too and I left it on over a long weekend when the temperature dropped to -35 here. It did not drain my battery enough to give me any problem starting on the following Monday.

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Excellent to hear. I wasn't sure if the little dongle kept trying to find a Bluetooth signal or something like that that would drain more than usual.

esse10 said:

Last time I parked my car and left obd2 plugged in for about 4-5 days the battery was drained by the 5th day I went to start the car, Hope yours is not the case.

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I should have him back up and cruising around on day 3, but I'll be sure to never let it go over that.

Thanks everyone!

esse10 said:

Last time I parked my car and left obd2 plugged in for about 4-5 days the battery was drained by the 5th day I went to start the car, Hope yours is not the case.

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Did you have a unit with reader/display attached or just a little blutooth device like we're using?

I did the same thing, 3 days and it wouldn't start.

I leave mine in all the time. No problems, though I too drive it everyday. If you have a good battery you shouldnt have a problem.

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mattyd2009 said:

I leave mine in all the time. No problems, though I too drive it everyday. If you have a good battery you shouldnt have a problem.

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If you're using the torque app I do believe there's a setting in there to auto power off. Not used it in a while but I remember something being there.

And the good battery doesn't make a difference, trust me. Mine drained out enough over 3 days to not have enough power for a good crank.

nighttrain1974 said:

If you're using the torque app I do believe there's a setting in there to auto power off. Not used it in a while but I remember something being there.

And the good battery doesn't make a difference, trust me. Mine drained out enough over 3 days to not have enough power for a good crank.

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What bluetooth device do you have?

This is the one I have that I did leave on my car for at least three days at -30 temperature.
Amazon.com: PLX Devices Kiwi Bluetooth Wireless Trip Computer and OBDII Scanner: Automotive

It has a little switch on it, so I can leave it plugged in all the time and only need to flick the switch to turn it off.

Also that is when my oil heater split in half (it was metal) and stopped working.

So on the 4th day the Beetle started from a -30 engine block with the battery having been drained some from the device.

I always try to remember to quit my Torque app as I'm getting out of the car, Torque does continue to try to reach the device if left on and drains the phone battery considerably. So perhaps if you left both running it would be why or if you have a different device maybe it's noisy.

What about if it comes with switch

My suggestion is to get one this device with switch which can seated firmly into the OBD port and expand its service life. similar as the link above, but much cheaper than that

find a good document, no more battery drain
How to solve ELM327 battery drain problem

5 days without running and one cold night and both batteries in my diesel were too drained to start the engine. A multitude of error codes resulted. I won't ever leave it plugged in again.

I've noticed now during the winter; if i have my elm327 plugged in all the time, the battery is lower and slow to crank in the morning. I pulled it off the obdII port and the next morning; my starter cranked better and it did seem to be battery drain, specifically from the elm327. My elm 327 does not have a external power switch or a auto power off feature; thus, can only assume it is on 24/7 and drains the battery. During the summer and warmer months; I have a left it plugged in all the time and it didn't seem to affect the cranking of the starter speed in the morning, that much, since it is not such a cold cranking situation and doesn't have the thick oil etc. to tax the starter, to the same degree.