Refurbished 4040 - So Far...

I just bought a refurb'd Maestro 4040 from Tiger Direct yesterday for
$99. Plugged it in on the way home and so far, so good!

One issue: the AC charger will not charge the battery but the car
adapter will. How is that possible? The unit operates fine from AC
power so what's the difference between the AC adapter and the car
adapter?

Also, and I'm only asking because I see a lot of resentment toward
Megellan in here, anyone know how to crack the unlock code for voice
activation?

Thanks!

~Dave