The LED belt battery pack accepts 4 AA batteries. Does it make a difference whether standard alkaline (1.5V) or rechargeable 1.2V batteries are used? Will the circuit be fine at 6V using 1.5V AAs?
its designed for either (there's a diode for keeping the voltage in the right range and polarity) but it might be just a tad brighter with alkalines. nimh are totally fine