I'm planning on using an ODB Bluetooth reader on my car and leaving it plugged in to use apps like Dash and Torque. It's a daily driver so I'm not that worried about depleting the car's battery, but I was curious how much amperage that port would suck.
I am not sure of your exact solution, but Brian Blum of Texas Instruments says the amperage draw depends on what state the device is in, of which there are seven states. According to the document in the link, it draws as follows:
- State 1 (wake-up) - 6.1mA
- State 2 (pre-processing) - 8.1 mA
- State 3 (pre-RX) - 12.3 mA
- State 4 (RX) - 22.3 mA
- State 5 (Rx-to-Tx) - 11.1 mA
- State 6 (Tx) - 29.3 mA
- State 7 (Post processing) - 8.1 mA
These are for the device listed in the document, but should be about the same. As you can see, these are very small amounts of draw. I would also bet, if you look at your device specs, when the vehicle is off, your device is off: no power consumption during this time. For your edification, it takes 1000 mA to make one (1) Amp.