An accessory for the "POWERTUBE" battery pack which has been presented by me in another instructable or any other battery between 2.7-11.8v.

What happens when the battery of your phone or mp3 dry out while riding your bicycle?

POLOLU S7V8A will do it's magic! For specs see here.

The S7V8A switching step-up/step-down regulator efficiently produces an adjustable output between 2.5V to 8V from
input voltages between 2.7V and 11.8V. Its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that start above but discharge below the regulated voltage. The compact (0.45″×0.65″) module has a typical efficiency of over 90% and can deliver 500mA to 1A across most combinations of input and output voltages.

See also the S7V8F5 with fixed 5V output if you're interested.

Step 1: Components needed

1x S7V8A module. See here for Europe.

1x 33μF/16V or larger electrolytic capacitor as recommend.

1x PCB prototype board (10mm x 52mm)

1x Female USB connector for PCB

2x 3mm orange LED (optional)

1x 33ohm ¼ or 1/8 resistor (optional)

1x Male 5.4mm power connector

1x Y-Cable 5.4mm with connectors (1 male to 2 female). See here.

1x Plumbing tube (54mm x 16mm inner diameter)

1x Acrylic piece (3mm x 19mm) or the outer diameter of the plumbing tube.

Cut a centered hole at the USB dimensions. Make sure the USB pass through the hole.

1x Acrylic piece (3mm x 19mm)

Cut a centered hole at the power connector's enclosure outer diameter.

<p>can this be &quot;hacked&quot; and mounted on the bicycle tire, maybe 2 of them in parallel to get +1A output.? its only $3</p><p><a href="http://www.ebay.com/itm/Hand-Crank-Generator-Dynamo-Emergency-USB-Charger-for-Cell-Phone-MP3-Gift-/321635908412?hash=item4ae2fe7b3c:g:UAYAAOSwpDdVLlV5">http://www.ebay.com/itm/Hand-Crank-Generator-Dynam...</a></p>