I've just recieved a Supernova but I'm not allowed to play with it till Xmas time. But I was allowed to read the instruction sheet.
It says "In the automatic mode,if you pressdown or discharge,the battery pack will automatically disgharge, then switch to charge, complete the charge, then switch to trickle charge".
It also states that you can only do this with Nicads because for NiMH and Pb batteries you have to tell it what rates you want.
As I said I haven't been able to play with it yet but thats how I read it.