FYI, when my scooter started doing something similar (in my case, running out of charge 2 blocks from my girlfriend's house at 2am during Orycon, despite having been plugged in at every chance during the time I was there), it turned out that the battery had gotten too old and needed to be replaced. Did that, and all has been well since. I understand they last about 2-3 years, and mine had been at least 5 years old, albeit 5 years of minimal usage except at cons.

FWIW, HTH, HAND!