In my frantic search for a simple and portable solution to "large memory" access on the 770, I stumbled upon the Apple iPod Shuffle Battery Pack . This little (literally, 2 AAA batteries) unit has a female USB 'A' receptacle on it intended for the Shuffle. I was intrigued by this as the Shuffle is intended to act like a memory stick and plug into your computer that way. It is also recharged by the USB, but the specs on the battery pack said that it would run the Shuffle while sparing it's rechargeable battery, but that it would not charge it. I was afraid that it meant that the Shuffle would run on 3 volts, the output of a pair of AAAs. From my experiments I knew that the 770 had to have at least 4.75 to recognize USB devices in host mode.

I decided to take the plunge and bought the battery pack as part of an accessory kit that Radio Shack sells for the Shuffle. Lo and behold, it produces 5 VDC! Closer inspection revealed a circuit board inside, so this unit must have a DC-to-DC convertor.

What you see is my quickie kludge to see if the box (1) could drive the 770 (4) and a memory stick (2). I have one of those adapters that takes an SD card and makes it into a USB stick--I have a bunch of those left over from my Palm days and you can see a 128 MB card in the holder. The cables (3) have their wires twisted together (red to red, blk to blk, etc.).

Now I am testing how long it will run. It has been going for almost three hours, i have the 1 GB card in it now and the movie on it has been playing for over an hour now.

My next step will be to wire everything up neatly and have ust a single wire out of the battery pack that will plug into the 770. The stick will just plug directly into the pack. It has a string lanyard attached to it that will come off and provide a nice clean hole for the 770 cable.

Nice setup there.... Have you tried to connect a USB Hard drive yet?

I don't own one (yet), but I imagine it would tax the AAA´s pretty heavily. I rarely fly more than two hours on a leg, so a 1GB flash holds enough movies for me. Also, the SD cards have dropped dramatically in price as well.

As Odin mentioned, unfortunately that's not likely to work.

A fair number of USB hard drives draw more than the 500mA that they are allowed - that's why they have dual USB connectors on some.

Assuming 500mA, most AAA rechargeables have a capacity of around 700mAh. That means that they can produce 700 mA for one hour.

Actually, that's not true. It probably means they can produce 35mA for 20 hours - they are less efficient if you drain them quickly.

Since you're approximately doubling the voltage, you're also doubling the current you draw.

So, if you have a 500mA hard drive, you're going to be drawing an amp from the batteries, which means they'd be dead in well under an hour.

I wouldn't be surprised to see them dead in 10 or 20 minutes, assuming that the DC/DC converter was able to sustain an amp.

For stuff like keyboards and self-powered hard drives like iPods, this is _great_. Good spotting. We should all look for other things like this, since I'm fairly sure that other people may make something similar.