Converting d cell batteries to 12v battery power

Long shot here fellas, ive got a portable stereo which takes 6 d cells - 9v. I'm trying to convert this to run off my 2nd battery.
Ive got a 12v cig adaptor with a switch to convert to 9v. I then wired both the positive terminals on the stereo to each other and then to the positive cig socket wire, and the same for the negative.
Should this work or am I smoking something?
I plugged it in and nothing happened, foot fault.
If no one can help I guess I'll just get some more batteries for my camping trip.
Cheers, Marcus

Marcus, I cant help with that wiring issue, but does the boom box plug into 240? if so you can get an inverter pretty cheap, and just think, the missus can bring her hair dryer camping!

If you're playing with electrics the first thing I'd do is grab a multimeter and make sure you are connecting positive to positive etc. Do it the wrong way around and it'll cause damage.

The second thing is to be sure that your 12V->9V adapter can actually deliver enough current. It might do the voltage just fine, but if the stereo is drawing too much current, the components that reduce the voltage from 12V to 9V in your adapter will overheat and it will die. The stereo should actually say what its power requirements in amps or watts are on the back. If it's drawing 18W, that means it will need 2A at 9V (because 18 / 9 = 2). Your power adapter should indicate how much power it can deliver.

Okay, so connecting them is a piece of cake. There's an end point in the battery cradle that should have a coil on it and that's the negative. Check which way around the power is using your multimeter and connect the negative poles together, then connect the other poles. Job done.

How to check which is positive and which is negative: that's also easy, with a digital multimeter. Set the multimeter to read volts, have the black lead in "COM" or "-VE" and put the red lead into "V", "+VE" or "mA" - don't use the 10A socket. Touch the leads together, the display should read 0.000V.

Now touch the leads to the power adapter's output - doesn't matter which one goes on what wire - and look at the display. If the number is NEGATIVE - showing, say, -9.252V, your RED lead is attached to the NEGATIVE wire.

It's as easy as that.

And if YOU already knew this, Marcus, my apologies. I'm writing it for everyone, and as we know, not everyone knows about multimeters!

Just make an extra long lead for it, drop the voltage right down

@ heath - that would be way too logical, easy and smart. I think it may also use more power that way?
@ Tony - legend, yeah not sure if you saw my other post, I went out and bought a multimeter, I'll do it tomorrow now and see where at, the plug is 10amp I'm sure the packet said. It's current is 800 mA I think.
The radio is 50 Hz 20w.
Pretty sure I wired it right way, but yeah gotta get up at 4am so I'll check tomorrow!
Cheers fellas! Gotta get it hooked up for Anzac day footy when I'm camping, go bombers!

If the radio draws 20W then at 9V it's going to need a little over 2.2 amps. You'd want a supply that could deliver 2.3A at a minimum, preferably 2.5A. Your 800mA unit will die very quickly.

The 10A mentioned is probably the socket and/or fuse that the device needs on its input side - the output is governed by what components were chosen to regulate the power.

Doesn't the car radio work?

digbyj said:

I then wired both the positive terminals on the stereo to each other and then to the positive cig socket wire, and the same for the negative.

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What two positives and negatives?

Old.Tony said:

If the radio draws 20W then at 9V it's going to need a little over 2.2 amps. You'd want a supply that could deliver 2.3A at a minimum, preferably 2.5A. Your 800mA unit will die very quickly.

Click to expand...

+1

the adaptor current rating is too small.


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Yeah, what I've done now is bought a basket and put a label on it saying "too hard" and I've put it in there. I'll just get spare batteries before I blow up something else!
Cheers.

Get an inverter

scottybobcat said:

Get an inverter

Click to expand...

or have a look in Jaycar, may have ciggy lighter adaptor to suit your load or one you can wire-up direct to power.




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