1. #1
    Forum Member

    Join Date
    Aug 2006

    Default Car Batteries & Cell Phones

    After the 12V battery is disconnected, I heard it said that it is possible for a cell phone plugged into a cigarette lighter has the capability of back feeding through the lighter and keeping the airbag capacitors from draining.

    Is this truth, myth, or safe practice?

  2. #2
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    nmfire's Avatar
    Join Date
    Nov 2002
    Maryland (DC Suburb)


    Truth which should lead to safe practice.

    Most halfway decent electronic devices will only flow current in one directions. Charge terminals are protected with diodes to prevent backfeeding current out through the charger.

    HOWEVER, its not like there is some tag or marking to indicate such. You don't know. I don't know. Nobody knows. Best practice is to always treat any and all supplemental restraint systems as armed. Even if you disconnect the battery and some book says they are drained. Big stereo systems can even have massive capacitors that could keep the air bag system energized.
    Even the burger-flippers at McDonald's probably have some McWackers.

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