http://blogs.technet.com/b/jamesone/archive/2007/12/14/usb-battery.aspx**Warning** Neither I nor Microsoft will take any responsibility for what happens if you follow these instructions. I am not recommending this, just reporting my experience. For ages now I've had a bookmark for a hack to make a "USB Battery" . I wroteen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)http://blogs.technet.com/b/jamesone/archive/2007/12/14/usb-battery.aspx#2662979Thu, 20 Dec 2007 13:52:48 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:2662979robincm<p>Swapping the 9V battery for 4 x AA (6V) would give you less voltage drop across the 7805 and so less wasted energy. Maybe get HF29G (Maplin) to hold them, think it also has a PP3-style clip. In fact, I reckon 6V is close enough to 5V that you could probably get away with no voltage regulator at all... but you can test that on your phone first!</p><div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=2662979" width="1" height="1">http://blogs.technet.com/b/jamesone/archive/2007/12/14/usb-battery.aspx#2650031Sun, 16 Dec 2007 00:06:10 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:2650031James ONeill<p>:-) I did a lot of soldering 20 years ago, and I do seem to have lost the knack of doing it neatly. Of course something to hold the bits while I'm working on them would help too !</p> <div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=2650031" width="1" height="1">http://blogs.technet.com/b/jamesone/archive/2007/12/14/usb-battery.aspx#2647767Sat, 15 Dec 2007 02:11:40 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:2647767josh<p>you need soldering lessons</p><div style="clear:both;"></div><img src="http://blogs.technet.com/aggbug.aspx?PostID=2647767" width="1" height="1">