Using ipod in numark idj mixer

I Just bought this mixer which is made for the ipod exclusively. I am waiting to buy to 30gb 5th generation ipods for it. My question is the mixer charges the ipods when they are in the docking station. I will only use this system once in awhile, so if the batteries in the ipods get discharged, will they still work because they are taking power from the charger in the mixer pod? I guess what I am asking is does an ipod operate like cell phones and other devices, even if the battery is worn out as long as it is plugged on to a charging device the ipod will still fire up and operate? Help before I buy Thanks Mike.