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Implications of having a OBD attached 24/7

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  • Implications of having a OBD attached 24/7

    What are the Implications of having a OBD attached 24/7 to my car pc?

    Or does it not matter?

    What if the car is running but the PC is off?

    Can any damage occur?

    Sorry if this is a noob question

  • #2
    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

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    • #3
      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.

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      • #4
        I Intend to install one of these and I'm OBD-II




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

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        • #5
          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
          If anyone gives me a rev - I give them the Bird

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          • #6
            I leave mine plugged up all the time. No Problems.

            BTW I have an OBDpros unit.
            2011 Nissan Frontier SL
            AMD X3 2.2 | M4-ATX | 16Gb SSD | 2GB DDR3-1333 | MSI GF615M-P33 MB
            OBDPROS USB | BU-303 GPS l LILLIPUT TS | Car2PC adapter | XM Direct | USB Dual band N with custom mag-mount antenna.

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            • #7
              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?

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              • #8
                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.

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                • #9
                  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
                  If anyone gives me a rev - I give them the Bird

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                  • #10
                    Also remember that USB is only 5 volts where as OBD is designed around a 12 volt system.

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                    • #11
                      Originally posted by Rick99TAWS6 View Post
                      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
                      Thanks Rick. This certainly sounds like the best way to fix it.

                      I'd rather not cut the wiring in the car. I read a description elsewhere about somebody who built a pass-through device, to sit between the OBDII cable and the DB9 connector on the scan tool, and switch the power from there. Perhaps I'll try that.

                      This issue got me by surprise. It will probably surprise some other n00bs inexperienced with scan tools. It's not quite relevant to the "What is OBDII" post in this forum. However, it might be genuinely useful if there were some FAQ type post where it was described.

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                      • #12
                        I was of the same mind about not wanting to cut the car wiring - but then reasoned that it(relay) was something that could be left in if I should ever have to sell the car, which is highly unlikely..............wife knows that the only way they will get the car from me is to 'pry the keys from my cold dead hands' .... just made sure it was a good wiring job

                        not sure that all cars have the OBD port powered at all times but probably should be added as a FYI in the FAQ
                        If anyone gives me a rev - I give them the Bird

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                        • #13
                          Originally posted by Rick99TAWS6 View Post
                          not sure why the automakers would not have the OBD power switched either....... of course then it was legislated by congress
                          The reason is that some tasks (especially reflashing the ECM) require a key-cycle, so the tool needs to remain powered even when the key is out of the ignition. It wasn't originally intended for streaming data to a CarPC.

                          Some non-ELM tools do things more logically. On the Mongoose we power from the USB port rather than the vehicle.

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                          • #14
                            Originally posted by samr7 View Post
                            I'd rather not cut the wiring in the car. I read a description elsewhere about somebody who built a pass-through device, to sit between the OBDII cable and the DB9 connector on the scan tool, and switch the power from there. Perhaps I'll try that.

                            This issue got me by surprise. It will probably surprise some other n00bs inexperienced with scan tools. It's not quite relevant to the "What is OBDII" post in this forum. However, it might be genuinely useful if there were some FAQ type post where it was described.
                            I think I'm having the same issue with my ElmScan5 USB.
                            When the ign is off the tool is still on, leds blinking and stuff.
                            My battery has drained a couple times, unable to crank the car after sitting overnight in the winter cold.

                            I'd like to have a relay shut it down via the pass-through method aswell.
                            Did you get a chance to do this samr7?

                            Anyone else want to chime in with this issue?
                            Sig, smig...

                            Ford Flex Toshiba Excite 7.7 Install

                            CoverMess - Cool Flash Covers

                            FlashFlex - Flash Components for your skinning pleasure

                            Mazda Millenia, Road Runner

                            YouTube - Road Runner, IGO8 PC, Dashcommand OBD, Visteon HD Radio

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                            • #15
                              I've experienced significant power drain at idle with a Chinese ELM myself. The device draws around 120mA with the engine off, that combined with the carputer idle draw doesn't let the battery last for much more than a week.

                              I've just been disconnecting it for the time being since current weather conditions don't permit me to work comfortably on my vehicle but a simple relay on the obd power wire should do the trick. Wired up as shown in the attachment.

                              The 30A rating of a standard automotive relay is overkill but they are cheap and readily available. Also, don't forget to put a diode across the coil (85 and 86) terminals to avoid excess voltage on the OBD line.
                              Attached Files
                              98' Honda CR-V
                              http://www.superbluecrv.com

                              *OBDMPG, the RR OBD Plugin*

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