I am buying a HUD Head Up Display. It goes in Sleep Mode when ignition is off (screen turns off). I asked the manufacturer, they said it uses 0.3mAh when in Sleep Mode (400mA while in use).

Is this enough to drain the battery? I know 0.3 is probably not a lot, but who knows. Manufacturer also suggested me to unplug it if I don't use the vehicle for a week+.

  • 1
    Does this answer your question? Do OBD2 Hud Head Up Displays use battery when engine is off?
    – Chenmunka
    Commented Oct 9, 2022 at 20:30
  • Not exactly, and I can explain why. So people say how OBD2 is powered on 24/7. If there is no device plugged in, obviously no battery usage. But if there is a device, e.g a Hud Display, how much power does it provide? As much as the device asks it to, or there is a constant and certain amount regardless? The OBD2 HUD I am buying claims it uses 0.3mAh while in Sleep Mode. I believe that's too little to be worried about, correct? But I am unsure whether my car provides only that 0.3mAh or more. I just don't know how exactly OBD2 works when something is plugged in, if that makes sense.
    – Antonis
    Commented Oct 9, 2022 at 22:39

1 Answer 1


If it really is 0.3mAh that it is using while in sleep mode, then this is what you will be draining from your battery. Chances are there are no weird features it will activate in your car's computer while sleeping. To be sure, of course, you could measure the drain on your battery without the device and then with the device plugged in.

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