I purchased an OBD2 Hud Up Display. Great reviews overall.

Manufacturer claims it uses 400mA when in use, and, what I care about; 0.3mAh when in Sleep Mode.

It goes in Sleep Mode when ignition is off. Now I know 0.3 is almost nothing, but I have a hard time believing it's THAT low. Not exactly saying manufacturer is not being honest but, 0.3mAh?

I also contacted them and they told me it's better to unplug it if I DON'T drive the vehicle for 1 week+. So if it's indeed 0.3mAh, why would they advise me to unplug it after a week when in theory it would take months, or years to completely drain a car battery at 0.3mAh?

What is your experience with OBD2 devices? Should I be worried to leave the device plugged in?

I mean I can always test it and have a nice jump start the next day, but I don't really fancy that lol. Plus I don't think it's good for the battery itself.

 

Matrix, a current draw that low is not going to have that big of an effect on the batteries. Granted, I do agree that 0.3mAH draw does seem a bit low. But, say overnight, I don't see an issue at all. If you are not driving the vehicle but once a week, then maybe ponder unplugging it.

I leave my OBD dongle plugged in 24/7/365 in my car with no issues. Now, I am starting my car almost every day. So, the pull from the battery is gonig to be minimal. Granted, it is not a heads up unit, but just a dongle to let me access the ECU when I want.

 

Matrix12345,
The manufacturer's claims are believeable. However, unless you lock your JLR vehicle, they have a habit of staying awake to all hours. A regular party animal.
Depending on where your device is connected, it may stay awake too. So, install the device, lock up at night and let us know how it goes. Maybe document your experience with a write-up and photos.

Note that end of trip voltage above 12.6V is what is known as a surface charge and will quickly dissapate.

Best regards,
Bill

 

Thank you guys.

I do know that 0.3mAh is practically nothing to be worried about, and in theory it would take months to drain battery, but I still try to make sure.

I think it is more that I have a hard time believing the device consumes only 0.3mAh whilst in Sleep Mode, as they say. It seems too low to be true, if that makes sense. So I wanted someone to confirm this.

It also doesn't help how they suggested me to unplug if I don't use vehicle for a week. Like, if it uses only 0.3mAh (which is nothing), why do you advise me to plug it off after a week of no use?

Thanks both of you for the responses.

 

Matrix, there is always the ultimate test, put their numbers to the test. You can tap into the power wires and see which one is still giving hte unit power. Once you know that, then you go inline with that wire and measure the current draw. For 0.3mAh draw, you would need a current draw of 0.3 milliamps. You get over that, then their numbers are bogus. But then, you can also figure out how long you can let it sit in your car and still be able to start it. My rule of thumb that I have found from playing with various vehicles is you can only take out about 10 AH before the vehicle will have a hard time starting. You get up into the 15-20 AH out, the car may turn over, but that is about it.

 

Sorry for potentially misunderstanding this, but are you saying that the wire gives a certain amount of power regardless (e.g 10mAh), or does it only give what the devices asks for specifically, in that case 0.3mah?

 

Power wires provide (or try to, subject to things like fuses) what a device uses, i.e. it's (almost entirely) up to the device.

You can think of it as a bit like water in pipes: there's plenty of water available but the amount flowing depends on how far you open the faucet (we say "tap").

(They likely mean 0.3mA. 0.3mAh is not how you'd normally describe a device.)

 

Thank you for clearing it up, JagV8.

However, if that is the case, why do some people claim (not in this thread of course) how their OBD2 device drained their battery in just a few days despite having a 'Sleep Mode'?

Basically they are claiming their OBD2 port is always live/hot (which is the case with most vehicles as far as I know anyway) and because of that, the device drained the battery. Pretty much saying it's not the device dictating how much power is being used, but that specific vehicle/OBD port.

In that case, are we talking about a faulty device that never really went in Sleep Mode, or just some people throwing false statements?

 

matrix12345, I am going to describe what JagV8 said in a different way. Think of a barrel full of water with a valve/tap in the bottom. The water in the barrel is the amount of power available. If you were to crack open the valve and let the water drip out drop by drop (a very low current draw like your HID system says it has), then draining that barrel would take a very long time. Where, if you have something that pulled a few amps (for example, or having the valve opened a lot more), the barrel would drain much faster. As for whether an OBD device could do that, this is up for argument. If you had just installed something into your car (what it is doesn't matter), the next time you went to start the car, the battery was dead. You remove the device and recharge the battery and never have any more issues, was it the device that you installed and then removed that was the source of the problem? Same argument those saying the OBD devices killed their battery.

 

Great analogy.

I have a good understanding now after all the comments. Apologies if this was dragged for too long, I just wanted to make sure before installing a device that could potentially kill my battery (which is not something permanent but I don't think any of us here loves jump starting a car, not to mention I don't think it's healthy for the battery itself).

I got the OBD2 HUD Display and so far so good. Goes into Sleep Mode the moment I turn the engine off.

Now how much power it uses when sleeping? Not sure.. Manufacturer said 0.3mAh, but who knows. I guess I will know if one day I wake up to a dead battery, hopefully that is not the case though lol. I also drive my vehicle (almost) everyday so I should be OK.

Thank you people for the time invested into this thread.