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Most dash cams don't have a large enough battery to record while the vehicle is off so most people recommend using an external power bank. However, to my understanding, most power banks with enough capacity for that purpose are not safe enough to leave in the car. Another option is to use an OBD to mini USB power adapter like this. But I'm not sure if that's a safe option either since most of these adapters appear to be of cheap quality. Any ideas on this?

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Maybe not answering your question completely, but: some people doubt how the OBD II connector is connected to power. The specification (SAE J1962 specification) of the connector is quite clear on this:

5.3.9 (...) Vehicle connector terminal 16 is designated Unswitched Vehicle Battery Positive and must be implemented in the vehicle connector. This terminal must be connected directly (i.e., unswitched) to the DC Positive of the vehicle's battery. This connection does not preclude the use of a fuse or other circuit protection elements. This circuit may be grouped with other similar circuits. This terminal must be able to supply a minimum of 4.0 A.

and

5.4 Vehicle Connector Terminal Protection — It is recommended that the vehicle manufacturer provide circuit protection in the event that the terminals of the vehicle connector are shorted together.

So yes, the OBD port's power pin (battery positive 16):

  • MUST be unswitched (always connected to battery power)
  • MUST be able to handle 4.0A (much more than any dashcam will use)
  • SHOULD be protected via e.g. a fuse

So except for the fact that you will/could drain the battery, connecting a dash cam to the ODB II port should not give any problems.

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    Welcome to the site. Great answer! – Zaid Mar 4 '18 at 7:30
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No, it's not a good idea to feed the camera from the OBD 2 port. Use the feed for the cigar lighter or another switched feed - fused with the capacity for what the camera will demand.

  • Thanks ​for the answer but my car is a lease so I can't make alterations. Any ideas about power banks? This one claims to be UL listed: amazon.com/dp/B01FN1Y7HW?th=1 @Solar Mike – k1sh83 Apr 20 '17 at 15:54
  • Why would you need an alteration? Just use a cigarette lighter USB power adapter, and plug it into the port. – GdD Apr 20 '17 at 16:23
  • nearly 2020, a number of cars do not come with cigar lighters anymore, or at least they are sometimes an option that people dont get – axa Apr 21 '17 at 0:48
  • @axa while some cars may not come with a cigar lighter any more, it is still not a good idea to feed a camera or any other accessory device from the OBD 2 port. Another source should be found without causing any damage. – Solar Mike Apr 21 '17 at 6:21
  • @solar didn't say it's a good idea to use the odb2 , it's a terrible idea, but another comment instructed to use the lighter and I'm just pointing out some cars don't have one. – axa Apr 21 '17 at 6:25
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A cigarette USB adapter as others suggested is the easiest method.

If you want to get a cleaner install I've used a piggyback fuse adapter yo install an ipod pre-amp to an OEM radio.

https://www.amazon.com/Circuit-ATC-Piggy-Standard-Holder/dp/B009K6U582

You just find a fuse that is powered when the car is on, like the radio.

It's got two fuses. One for the original fuse and one for the new device. I'm pretty sure the original fuse powers the new device fuse so if you keep the original the same the circuit will be adequately protected.

It should be easy as long as the additional device isn't too much for the circuit you're piggybacking on and blows the fuse.

  • Great answer. I was looking for an example like that so thanks for posting an example of the exact product. – raddevus Nov 13 '17 at 21:30
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No, that's bad because it blocks off the OBD2 port and the wire could get knocked out. You could splice in behind the port if you know which wire is switched 12V though.

If you just want the thing to run off car power and turn on and off with the ignition, you should splice into a switched power line under the dash- if there's nothing conveniently close to your install location, you can always just directly splice it in under the steering column and run a wire under the dash to wherever you need it. If you're trying to install something on the ceiling near the rear view mirror, I find there is plenty of hollow space in the pillar around the windshield (makes pillar mount gauges with lots of wires very easy, certainly enough room to run power for a camera).

If you're trying to run the camera after the ignition is turned off, you might want to wire up something like a turbo timer- ie, a power supply directly connected to the battery that listens on a switched power line and then waits a configurable period of time before turning off the circuit. This way it doesn't drain the battery to death but it still runs for some period of time after you remove the key (during an accident for example). This is an actual electronics project tho.

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The radio has an always hot wire that runs the clock. Use it to power small devices. I think on GM it's the pink wire going to radio.

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There is a new option with the powered OBD. Now they pair it with a proximity radar which only draws power when and where an object comes within 3-5 m of the car, and auto switches off when there is no subsequent movement.It is also paired with an on off switch. Presumably, this deals with the issues of overdrawing from battery after the ignition is switched off. The plug and play nature of an OBD based power source, and a 12V to 2V step down is a great USP

  • Thanks. But my problem is not overdrawing the battery. I'm wondering whether it is "safe" to do so; e.g., whether it can cause short circuits, or it can mess up with the car's computer system, or it can cause permanent damage to the the car, etc. – k1sh83 Mar 15 '18 at 2:55
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Regarding the OBDII port, another answer here provided a very good explanation of why the connector could power the device, however I'd like to add the following:

As this connector is unswitched, the dashcam will not properly cycle on/off with the vehicle. I would recommend against using the dashcam on an OBDII port unless you have some way of signalling to the dashcam when it should turn on/off

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Try a BlackVue Power Magic Ultra battery. It's a battery bank can be hard-wired, simply plugged into a cigarette lighter, or plugged into a USB-converted cigarette lighter. If you decide to hard-wire it, it comes with fuse tap connectors to hard-wire it into your fuse panel, so no need to snip wires and such. Then the battery bank is charged while driving, and it powers your dash cam when you're parked so it'll never draw off your parked battery. It's pricey, but I say it's worth it for preventing battery issues.

It also comes in handy where if you need more power, you can sequence up to four battery banks together. So it can be an added bonus to use for any application - for example, it can be used for power when travelling on a road trip with the camper. Overall, I recommend this external battery pack as it's a simple install and has uses elsewhere when needed.

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If you cigarette lighter is always on, you can put in a male to female lighter adapter with a low voltage cutoff switch and then a cigarette lighter to usb adapter to your dashcam. This rig will kill power to your dashcam if your battery drops below 11.6 volts. The easiest to find m to f adapter with the switch built in is made by Koolatron (it's called a "battery saver" and available on amazon). If your cigarette lighter is only powered when the engine is on you can use either of a couple of obd power supplies on Amazon and with a similar switch and they are very inexpensive. So I would not just kludge in a couple of wires to my obd port. When parked you would only want the camera in standy mode or surveillance (using g-force activated camera or motion activated camera) If my lighter only worked when my engine was on I'd set up a single USB line from the dashcam to a point under my dash, then I'd use the OBD port adapter when I needed to (when the engine is not on), and a cigarette lighter when the engine is running. If my cigarette lighter was always on, I'd use a heavy duty splitter (rated at 10 amps mimimum), plug the Koolatron battery saver to one port, plug in a great cigarette lighter to usb adapter to the Koolatron, and run the wire to my dashcam while retaining the ability to charge phones etc from the other port.

No problem when you need to use the obd port just pull out the adapter and plug in the scanner. You will not be taxing the power of the OBD port, which is meant to supply up to 4 amps even the dual dashcams spec out at 2 amps or below.

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I bought a buckline which plugs into the obd2 and it worked really well the dash camera has a fail safe so not to drain the battery if left for a long time. I went to buy another and couldn’t find anyone selling them so I began to wonder if they were not a good option. Today maybe coincidentally I had the engine light come on so I checked the code and it was supposed to be a sensor. I stopped at home and disconnected the buckline and then the car battery for over an hour. Just connected the battery again and the engine light went off. I’m going to try driving for a while and see what happens. If the warning light comes on without the camera I guess it was just a coincidence

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