Leave ODB-II Bluetooth dongle in?

Same question, is the power draw from this a problem?

 

I just leave it in, i doubt it's anything more than a few watts..

Just don't leave it in the car and park it for a month or something..

 

All of the other cars I have owned have the OBDII port powered at all times and I would assume likewise for the Prius. Whether or not it is a problem really depends upon the current consumption of your particular device and how long you're likely to leave the vehicle un-driven. Most of the OBDII Bluetooth modules appear to have a sleep mode that reduces current consumption when the vehicle isn't running. However, the sleep mode current load can vary from 1 mA to over 20 mA, based upon a quick survey of various OBDII Bluetooth modules.

The following article calculates that the normal 36 mA load for an unpowered Prius will permit the car to sit for 32 days before the 12 volt battery is drained. It's a linear function, so if your OBDII device also draws 36 mA in sleep mode, then the battery will be drained in just half the time... 16 days. For a 10 mA OBDII device, your battery will last 25 days. Of course, all of these calculations assume a fully-charged relatively fresh battery that still performs to spec.

Leaving a Toyota Prius Undriven

Your biggest challenge is going to be determining the current consumption of your specific OBDII device... most of the manufacturers don't provide the data.

 

I've had my Bluetooth ELM 327 device plugged in since the middle of March with no ill effects.
I may go a couple weeks & never use the Torque app but when I want to check something it connects fine.
If I am making a lot of short trips & want to always monitor something I've found it best if I exit/quit the Torque app on my phone before powering down the Prius. Then when I power the Prius up I can usually just start Torque again & it will work.
At times I do have to power-cycle my phone before I can connect.

 

I had mine in for almost a full year in the PIP with no problems... removed it when I sold the car.

 

Same experience for me. I plugged my ELM 327 adapter into the OBDII port when I bought it last fall and it has stayed there ever since. No noticeable difference in battery charge level but I drive my Prius almost every day.

The only issue I've had with the ELM 327 plugged in is that my bluetooth phone does not ring when I have an incoming call (specifically, no sound is played through the speakers). I can see that I have a call on the MFD, my cell phone vibrates and I can speak with the caller and then hear them through the speakers when I answer the call. Kind of strange but that's how it is.

 

If you drive regularly, it will be fine. I wouldn't make it a habit of leaving it plugged in for more than a couple days without driving the car. Although the battery can go several weeks before it's drained flat, the state of charge should not be allowed to drop much, otherwise damage to the battery will accumulate.

 

I've got a KIWI with an on - off switch and a couple of times when I've forgotten to turn it off an ABS brake warning light will come on and the brakes will act strange until I turn off the Prius and turn it back on with the KIWI turned off. It is a little scary since the brakes feel like they aren't working correctly. I've seen other threads here about the same issue. I try to turn it off every time now!

 

A similar glitch happens with my ELM327 bluetooth adapter from Ebay that's always plugged in. If I don't shut down the Torque app when I turn my car off and then return to start it (after stopping at the store for example), I'll get the ABS brake warning light like you. As long as I remember to shut off Torque I don't have any issues.

 

Just be aware that if it's left plugged in then your car is open to hackers. Someone who's skilled could cause a lot of damage.