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I have a question about a 12 V to 12 V isolated DC-DC converter.

I am trying to connect a Bluetooth adapter to my old Becker radio, but I got some annoying noise when it was connected. It turned out to be a ground loop, so I bought a 12 V to 12 V isolated DC-DC converter (B1212S-1W).

Today I connected it and after I turned the radio on the DC-DC converter just smoked and got super hot, so I guess it's toast now.

I connected it using the following diagram:

12v dc dc converter

I connected GND (pin 1) to the main ground of the car and the Vin (pin 2) to the switched positive on the radio. I then connected -Vo and +Vo to the Bluetooth adapter's ground and positive cables.

I guess I somehow shorted it, but shouldn't the wiring be correct that way?

I also saw this video and in the end he said it should be connected in series (the same as I did).

Sorry for the late reply.

There was only this bluetooth module connected to the converter. I just measured it and on startup (where it draws the most) it only has a max amperage of 20 milliamps, so that shouldn't cause this issue right? After a few seconds it drops to 0 amps on the multimeter.

Edit: Are there any other 12v to 12v isolated dc-dc converters for cars? Because when i search i can only find these things.

Many thanks!

SamGibson
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nasty12312345
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  • Are you sure those were the ground and 12V rails for the radio? – Hearth Sep 29 '22 at 15:45
  • nasty12312345 - Hi, You posted an "answer", but it was still asking for advice. Therefore it should not have been posted in the "Your Answer" box and it has been moved into the question as an edit i.e. as an update instead. *Unless* you are writing the *full & final conclusion* to your own question, without using any other answers (i.e. unless you have solved the problem totally on your own & with no further help needed) please don't use the "Your Answer" box below. Instead, you should edit the question to add new information or updates etc. See the [tour] and [help] for more rules. Thanks. – SamGibson Oct 02 '22 at 23:44
  • (Or if you are responding to an answer to request clarification, to raise a concern, or to add a minor response which is only of relevance to that answer's author and not to anyone else trying to answer your question, you can [write a comment](/help/privileges/comment) below that answer (on your own questions only, until you have 50 points). FYI here is the main [commenting policy](https://meta.stackexchange.com/questions/19756/how-do-comments-work).) – SamGibson Oct 02 '22 at 23:47

2 Answers2

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The connections would appear to be correct. You should check that the 1W rating is enough for the adapter. The 18V surge rating is not enough for long-term reliability on an automotive power bus, but still I would not expect it to fail right away unless you (even very momentarily) got the input power polarity wrong or (possibly) shorted the output.

You can check with a new one by just powering it up and measuring the voltage before connecting anything. It will read a bit high with no load, maybe 13 or 14V, so for a full check put a 1K resistor across the output.

Spehro Pefhany
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That converter is short circuit proof per the data sheet if it has the "R2" suffix. Be sure it failed, now that it is cold connect it with a 10mA load and see if you get your 12V with the recommended capacitors connected and see if it stays cool. If not you may be able to get a refund or replacement. The converter is 83mA maximum steady state load with a max surge capacity of 100mA, that does not sound like enough to run the bluetooth device especially if it has speakers.

The data sheet states you must have at least 8.3mA load (~10%). You need to connect the required capacitors as stated in the data sheet.

Gil
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