Making a "Pedal Juice" out of USB Backup Batteries

Frequently asked questions regarding powering your pedal.
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Yonatan
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Post by Yonatan »

I've been eyeing the Pedal Juice (switching adapters create a bad hum for me), but I have a couple of these USB backup batteries around and got this idea. Each one is rated at 5V/1A/5W, so I strung the two together just as a POC.

It is putting out 10-11V, so I should probably add a voltage regulator to be on the safe side (though I did read that the Boss PSA puts out 9.6v...) What do you all think? And is there any low-tech solution for dropping the voltage (diode? series resistor? voltage divider?) Or should I go all out and get a voltage regulator for it?
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Yonatan
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Post by Yonatan »

I ran into a glitch:

It turns out that after pressing the power button on each of the batteries, they power the pedal just fine for 10-15 seconds but then they both shut off. It's like the batteries don't think that they are charging any USB device (which they are not...). If I plug my iPod into one of the batteries, then that battery stays on continually and provides power to the pedal as well.

Does anyone know how to "trick" the battery into thinking that it is charging something? Something to do with the D+/D- pins (I left them floating)? Or maybe the pedal is just not drawing enough current (it's an Electra Distortion) for the battery to think it is being used?

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Yonatan
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Post by Yonatan »

To answer my own question, I connected the thing to two pedals using a daisy chain cable, and it stayed on! So my theory about this USB battery is that after turning on the battery, the battery's circuitry tries to detect if current is being drawn. Since an Electra Distortion probably only draws a few mA, it was under the battery's radar.

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