Thread: Implications of having a OBD attached 24/7

I do that all the time, most of the interfaces use very little power so leaving your interface connected will most likely use less power than needed to keep you clock/radio etc powered in standby.

Paul
www.obdpros.com

If the car is running with the scanner turned off, it's safe. Some OBD-I scanners require an additional hook up to battery power, OBD-II scanners draw their power from the OBD-II connector. The diagnostic link connector only has power to it with the key in the run or start position. If your OBD-I scanner is connected to a hot at all times circuit (not switched power) there may be a draw on your battery. Some car cigarette lighters are hot at all times, some are switched.

I Intend to install one of these and I'm OBD-II




http://cgi.ebay.co.uk/ws/eBayISAPI.d...ayphotohosting

I dont have the same interface - but I am using HPTuners on my carpc for tuning/guages/diagnostics and have found that if the car sits for about 4 days without starting the HPTuners interface will pull the battery down - course then I plan on getting an Optima someday when the current battery dies. I ended up putting a switch in the OBDII power line on my car just in case it is going to sit for awhile - no problem for me during the warmer months with the car sitting much though

I'm bringing this post back to add an observation.

Apologies if this seems obvious, but it sure wasn't to me!

I got a new USB unit from obdpros.com yesterday, and hooked it up for the first time. It is not visible on the USB bus when USB is connected but OBDII is disconnected. When OBDII is connected, its LEDs light up and it becomes visible on the USB bus. The part that came as the least pleasant surprise is that its LEDs light up so long as the OBDII is plugged in, regardless of the car's ignition.

I hooked it up on a test bench, and apparently it draws 60mA at 12V.

Why on earth would these devices not be powered over USB or RS232?

Why on earth would these devices not be powered over USB or RS232?
I think this is obvious. These interfaces are not designed to be left in the car 24/7.
Besides that, with the engine running there's no problem of exhausting the car's battery.
This makes the PC's battery last longer.

Well as I said above I am using HPTuners MPVI Pro for tuning/gauges/diagnostics and should have included scanning/logging. It is capable of stand alone logging without being hooked up to a computer - use this feature to log other cars for later data evaluation on one of my PC's, usually the carpc though ..... Therefore it can be powered by either the car OBDII port or the computers USB port - but I would imagine that they would use the OBD power since there is a lot more available(USB only has about 5 watts available I think)

I have hooked a relay to the cars OBD ports power wire which is switched on/off via a power wire only on when ignition is on, gets rid of the drain when the car is not on from the interface(dont want/need it on 24/7) - not sure why the automakers would not have the OBD power switched either....... of course then it was legislated by congress

Also remember that USB is only 5 volts where as OBD is designed around a 12 volt system.