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

[tomchr at ee.washington.edu]

Ron,

Just FYI: Replacing the car battery with a 9V battery won't turn off the power to the car. Some circuits will still be hot... But in the event something does go wrong and you have a short circuit, the damage will be much smaller. You can pull enough current form a car battery to weld steel (100's of amps). If you get more than a few 100's of mA form a 9V battery I'd be surprised. Not enough to cause any significant damage to the wiring or chassis.

But in the long run, I'd suggest getting that radio code somehow.

Tom


On Mon, 27 Jun 2005, Ron Wainwright wrote:

>  Tom,
>
>  Reply inserted below.
>
> --- tomchr at ee.washington.edu wrote:
>
>> 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
>
>
>  I bow my head in the presence of your E-mail!!
> Exactly what I was looking for.
> Thanks
> Ron
>
>
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