How can I make a 12v ~2.3Ah battery to work with a 9v ~>2Ah device

[liviuile]

I have a Line 6 microspider sound amplifier that work at 9v 2000 mAh minimum. I also have battery 12v 2.3Ah that I want to use it for the amplifier. How can I make that battery to deliver 9v?
Please, I need it for sing on the street.

 

[Resqueline]

You mean it runs on a 9V AC 2000mA adapter as an alternative to its internal 6 x 1.5V batteries. AC is different from DC.
The 9V AC would be internally rectified, producing around 12V DC. So imho you can connect the 12V battery directly to the 9V AC input. Polarity won't matter.
Just put a 2-5A fuse in one of the wires from the battery for (fire) safety in case of a short at the 2.5mm plug.

 

[liviuile]

Yes, it's runs on a 9v 2000 mA adapter. i used it as you say it for a month, and it worked ok. But now it won't start on that battery when I put it to AC input... But on it's adaptor work fine...
i was thinking to put the 12v battery in place of those 6 x 1:5v batterys... i really don't know how to make it work, and I relly need it...

 

[Resqueline]

So what you're saying is that you did connect the 12V battery to the 9V AC input, and it worked for a month?
And then it stopped working off the battery, only working with the AC adapter?
Are you sure the battery wiring & plug is still ok? If so; try to reverse the battery connections (polarity).
If reversing the polarity makes it work then there's a chance the internal rectifier has gone bad, and needs to be replaced.

Yes, it should be possible to connect the 12V battery in the battery holder instead, but I can't guide you there without a picture (or two) of the battery case.

 

[liviuile]

http://img522.imageshack.us/content_round.php?page=done&l=img522/2329/13102011477.jpg

i already reversed the polarity, but still not working...
I heard something about a voltage regulator... But i don't know these thing... I'm a musician not a fisician

 

[Resqueline]

Ok. I'd suspect the wiring or plug being faulty then. Is there any way you can think of to check if you have power all the way to the tip of the plug?
The picture I had in mind was of the 6 x 1.5V battery holder/case of/in the amplifier. Sorry if I was unclear.
Yes, one could use a regulator to lower the 12V to 9V, but I don't think that's neccessary here.

 

[liviuile]

http://img687.imageshack.us/content_round.php?page=done&l=img687/3631/13102011478.jpg

wow!!! I checked the cable (the plug)... and it was broken...
My BIG question is:
CAN I SAFELY PUT A DC (BATTERY) IN THE AC PLUG??? A friend told me it is a mistake... Thank you for all your help!

 

[Resqueline]

Hehe, glad you spotted the problem.
Sometimes DC into AC it can be a mistake and damage something, and sometimes it just won't enable the device to work properly, but in this case it's no problem at all.
The designer may even have made it like this on purpose to avoid problems with people using wrong polarity adapters, and also to enable trouble-free 12V use.

I see the battery holder is a loose item, and there seems to be enough room for you to unscrew the holder and put the 12V battery in there instead.
Then you'll have to connect it to the red (+) & black (-) battery holder wires somehow, and also fasten & insulate it so it doesn't move around and short out.

 

[liviuile]

ok. So, the battery work in both inputs (ac and dc -in place of those 6 x1.5v batteries). Thank you!
Is it safe? It won't burn soething there because is it bigger voltage?
And last, where is better? In the ac plug, or in place of those 6x1.5 v batteries?

 

[Resqueline]

My electronics experience tells me that an amplifier made like that (9V AC & DC) is likely to be very tolerant of supply voltages, probably up to 16V.
But of course since I haven't seen the actual shematic diagram or the circuit itself I can't give any guarantees.
Using the AC plug is electrically safer, but more vulnerable to physical damage as you have experienced.
Using the internal battery connections is very convenient & physically safe, but electrically risky in that a polarity mistake could result in damage to the amplifier.

 

[liviuile]

thank you very much for you answers and advises. I will use internal conections for my battery. I will be very carefully to the red/black wires not to mistake them.
Have a nice day!