[V6-12v] first problem sooner than later***Updade***

[tomchr at ee.washington.edu]

Argh!!!! Connecting a 9V battery to the 12V system in the car will likely cause the 9V battery to get really, really hot. I would not be surprised at all if it exploded!!

To avoid battery explosions, connect a diode in series with the 9V battery. Any silicon small-signal rectifying diode should work. 1N4148, 1N4007 (or any diode in the 1N400x series) should work just fine. You can get these diodes at Radioshack - or any other store dealing with electronic parts.

The diode has two pins - anode and cathode. The cathode is marked with a band printed on the body of the diode. Connect the cathode of the diode to the center pin of the cigarette lighter plug and connect the anode to the plus terminal of the 9V battery. Connect the minus terminal of the 9V battery to ground (the outer ring of the cigarette plug).

The diode will block 12V from entering the 9V battery but will allow current to flow from the 9V battery to the circuit in the car once the 12V is disconnected.

Tom


On Mon, 27 Jun 2005, Kent McLean wrote:

> Ron Wainwright wrote:
>>  I thought I heard some were that you can make or buy
>> a small power supply to keep the radio from going into
>> SAFE mode when disconnecting the battery?!
>>  Kent do you know??
>
> I think a 9V battery (the rectangular kind) works; borrow
> one from a smoke alarm. IIRC, take a cigarette lighter plug,
> attached the wires to the 9V battery, and cross your fingers.
> 'Tis best to have the code, for when the battery dies.
>
> Some people have found the code in the trunk, either hand
> written or on a sticker.  Look around, you may get lucky.
>
> --
> Kent McLean
> '94 100 S Avant, "Moody"
> '89 200 TQ, "Bad Puppy" up in smoke
>
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