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Possible to turn an AC device into battery power? Answered

Hi, Ive been searching the internet looking for a way or to know if it is possible to turn a device that plugs into an American outlet able to run off of batteries. The device I am talking about is this: http://www.guitarcenter.com/DigiTech-Vocal-300-Vocal-Effects-Processor-101559516-i1124234.gc from the picture it shows where to plug in the power source saying: 5V AC 1:3A Is this possible to make something to connect to it and run battery power? Sorry my knowledge of electronics is lacking!



8 years ago

When I zoomed in on the power jack on the picture, I could not tell exactly what voltage is stated. I looked like it could be either 5VAC, 1.3A or 9VAC 1.3A. This device most likely comes with a "wall wart" that converts 120 VAC to the lower AC voltage.

Although I can't state this with certainty, it most likely rectifies this lower voltage AC inside the unit, to produce the DC needed for the electronics. If my assumption is correct, you should be able to feed DC into the jack. The DC votlage to use would be about 1.4 times the AC voltage stated on the panel, as the AC number would refer to a RMS value. So, if it needs 9VAC, use a DC voltage of about 12.6 volts.

A second method would be to use an inverter, along with a 12 volt battery. I have seen very small 12V DC to 120VAC inverters that plug directly into your car cigarette lighter that can output 40 watts, for only about $25.


Reply 8 years ago

Thank you for your reply.

So basically if I buy an inverter I can hook up a 12V battery to that, and then connect the inverter to the device with the standard wall outlet plug?

I know batteries have different Ah, but I dont know the formula for determining how long the battery would last with that devices power demand. If I wanted a battery to last say for about 5 hours, what specifications for the battery should I be looking for? The other question I had about the batteries when I searched for "12V batteries": there are some 12V batteries that resemble small car batteries and some that resemble a larger 9V looking battery, Im looking for something compact and not 20lbs.. why are there much different batteries, Im assuming it has to do with how long they will last?


Reply 8 years ago

Yes, you would connect the 12v battery to the input to 12 volt input to the inverter (which is often a cigarette lighter type plug) and the inverter has an outlet that looks like a standard 120 volt outlet.

The power consumption specs on the unit probably refer to the maximum. The typical current draw is most likely less than the 1.3 amps stated on the unit.
1.3Amps at 9 volts is 11,7 watts. Inverters are fairly efficient, but of couse not 100%. Maybe conservatively assume that they are 75% efficient, so your 12 v battery needs to supply about 15.6 watts maximum. If the battery voltage is a constant 12 volts, this translates to a 1.3 Amp DC current draw.

This is where is get difficult to size the battery for your approximately 5 hour desired time. Just multiplying the maximum DC current by 5 hours gives 6.5 amp hours, which might weigh about 5 pounds if it is a sealed lead acid type.

I think you could get by with a battery with a lower amp hour rating, but I can only speculate, as I don't know the typical draw. Places like batteries plus or online places like Digikey have a good selection of 12 volt sealed lead acid batteries with various amp hour ratings.

Hope this helps.