Alpine CDE-102 keeps iPod awake until battery drains
Solution 1:
I've found that with my 5thGen iPod (30GB Video, same as yours) that if I hold down the "pause/play" button, it goes into a deep-sleep mode (display off). Then I quickly push the "lock" switch so that I don't turn it back on.
This seems to work well for keeping my iPod charged up.