BASIC BATTERY QUESTION voltage drop in imitation LED

[rambo180]

Hi, please excuse me if this is a silly question(s). I recently purchased a quite bright 3D cell LED torch from a Bangkok market (it looks a lot like a maglite but much brighter and projects the image of the diode on the wall at full zoom). So questions please: If I put in used duracell alkalines (around 1.45V each) will that lessen the output compared to new batteries? Is it likely that this light has a resistor that limits the voltage flow to the LED (at 3.6V or 4.2V - i'm not sure which) ? So any voltage (total from my batteries = 4.35V) above, say 4.2V, is wasted? Or would a torch like this not have a resistor?? Is it likely to have a similar LED and resistor setup as a brand name 3D such as the LED Lenser P17? Do LEDs generally operate in a maximum range voltage and drop dramatically, or is it a slow light output drop? Eg: 4.5 to 4V = best output 4V to 3.5V = slightly less output anything less than 3.5V = but new batteries? Should I also be considering current output in my thoughts? Will the duracell alkaline drop quickly below 1.4V or will they sit at that voltage for half the life of the battery? Would you bother buying a cheap ($25) 3D cell LED or would you purchase a brand name for heaps(?) more money? THANKYOU!! very much, any info you know is very useful. thankyou again!!!