Author Options:

powering car stereo from computer PSU. how to keep settings?? Answered

hello. i am using a high end car stereo, powered by my compouters PSU. i have sorted the red and yellow cables from the head unit, so it powers, but the problem is, that everytime i turn off the computer the car stereo looses settings. Since no one has done it on the instructables i have seen, i guess its hard to be done. has any one done it? i dont want to have the PSU 24/7. i would prefer an external battery...



Best Answer 5 years ago

The car stereo should have (at least) two +12V inputs. In the automotive world, there are (mostly) fixed contact numbers for them.

Contact 30 is the permanent power that is always connected to the battery. (your stereo needs a battery here)

Contact 15 is the switched power, that is only on, when the ignition is on.

So, what you can try is:
- get a small 12V lead battery.
- connect the PSU directly to contact 15 of the stereo. (This will power the stereo)
- connect the PSU to the battery via a diode (make sure, the battery is precharged or invest in a charge controller) The diode will stop any current from the battery backwards through the PSU if the PSU is switched off.
- connect the battery to contact 30 of the stereo. This will preserve the settings if the PSU is switched off. You may want to put a diode between battery and stereo to prevent current bypassing the charge controller.
- off course, connect all ground pins i.e. minus of the battery and contact 31 of the stereo

Thanks! this seems like it would work.. but its "allot" of work. i was wandering, wouldn't the 5v standby (purple) from the PSU work??

I may be wrong ,but it seems to me that a radio's settings memory would be like a computers bios memory in that it doesn't require a big high amp battery to maintain settings when the power is off.

I suggest using a 23A size battery which is 12 volts. they are used in garage door opener remotes. Just make a battery holder for the
23A battery and connect it only to the permanent power pin
or whatever pin is for memory.

Note: "23A"  is the actual battery size.  It does not  mean 23 amps.

That should work. Just put a diode between plus of the battery and the permanent power input (contact 30) of the stereo. If you can't get a 23A battery, you may try 8 AA cells in series.

Use a couple of diodes to connect from your PSU and your battery.