It works with 4 batteries to power the amplifier giving high volume level, ideal for outdoor use.
It can also work without batteries with a volume suitable for indoor listening.
more photos here
Step 2: Placement
The 4 batteries compartment has the ideal size to place the iPod.
The single batterie compartment has the size to put 4 AA batteries
Step 3: Soldering
Soldering the wires for the new 4AA batteries.
The wires are attached to a connector with two pins. (the ones used to power hard drives) the connector will make easier to remove the batteries.
The two pins I tested as working to power the amplifier are the bottom (pin 5) and the middle (pin3)
I came to this conclusion using the trial and error method. (with the iPod connected to the line-in, tried the batteries cables to one pin (red) and connected the other cable to the other pins until it worked)
Step 4: Connecting the batteries
The holder comes with a connector, but had to cut it and solder the male connector that fits to the one used on the trensformer. (from an old hard drive)
Step 6: IPod fastener
The velcro band is one of those used to bundle wires together. (a rubber band could be used also, but it isn´t so easy to remove)
Showing the iPod and the cable which will connect the headphones port to the radio line-in (phono/phone)