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How do you hook up a battery and PC power supply and a 12v car stereo ? Answered

Hi there I am putting together a diy boom box but cannot figure out how do I can nectar a 500w PC power supply and a 12v battery up so then I can use both of them to use the boom box I've figured out how to use it with just the battery but unsure on how to with the PC power supply please help



Jack A Lopez

1 year ago

I think it would be convenient if you had some way to connect your amplifier-music-player thing to either the 12 volt battery, or to the 12 volt DC output of the power supply, but definitely not both at the same time.

I think a switch (like a slide switch or a togggle switch) would be the most attractive way to do this.

Also on the subject of switches, I think the PC power supply has a signal line it wants pulled low, just to get it to turn on. So a switch would be handy for that.

Since you want to switch two things at once, a double pole switch would be appropriate. This switch should also double throw, since one of the things to be switched is, connecting the positive terminal of the load (the amplifier-music-player thing) to either the positive terminal of the battery, or the +12 volt rail of the PC power supply.

Anyway, I can sort of picture, in my mind, how this would all be wired together: the DPDT (double pole double throw) switch, the amplifier-thing, the 12 V battery, and also the {black, yellow, and green} wires from the PC power supply.


I do not know if you also can see this picture. If you do not quite see it, just reply to this post, and I will draw a picture (a wiring diagram) of it for you.

18R4H1M.Jack A Lopez

Answer 1 year ago

Hi thank you for getting back to me. I've figured out how to connect everything up but unsure of how I connect the PC psu to the battery just for it to charge when it dies

Jack A Lopez18R4H1M.

Answer 1 year ago

Most of the time, charging a battery is more complicated than just connecting the battery to a power supply.

Whenever someone me asks a question about charging batteries, I direct him or her to this page,


specifically, the section titled "How to Charge Batteries"

I mean, it is kind of complicated. Although some kinds of batteries are less complicated, and some charging methods are less complicated. In particular, slow charging seems to be less complicated than fast charging.

For example, a sealed lead acid (SLA) battery can be slow-charged with constant voltage, in series with a resistor, or maybe just in series with the internal resistance of the battery itself.


But maybe this leaves you wondering, well, "How can I build a practical boom-box, that will work for different power environments (e.g. outlet nearby, no outlet nearby)?

And I don't know the best answer to that.

Maybe it would be better implemented as a sort of big toolbox, with plug-in battery charger, with two swappable batteries, of which, one is always charged. Also, you do all the DC power to the amplifier-thing with plugs (instead of switches), and also put the PC power supply in the toolbox too, with the same shaped plug on its 12 VDC output, so you could use it to power the amplifier-thing, for circumstances where there is outlet nearby.

Did I mention slow, floaty type, chargers for 12 volt SLA batteries can be found cheaply? Especially if there is a Harborfreight(r) store in your town.



1 year ago

I'm a little confused by your question, if you've already figured out how to power it from just the battery then why is it part of the question?

If you want to use the PC PSU with a 12v battery (but why would you?) you'll need an inverter.

If you want to use the PC PSU on mains power you just need to identify which of the PC PSU outputs are +12v and which are ground, then use those to power the boom box. Check out some of these I'bles for tips on identifying the pin outs of a PC PSU.



Answer 1 year ago

Hi thank you for getting back to me. I've figured out how to connect everything up and now wanted to add a PC power supply to charge the battery when it dies but don't know how I should wire it up with the rest of the stuff