Oh wow, I'm confused! I'm still in the beginning stages of learning about resistors, LEDs, milliamp-hours, power draw, etc. so I apologize if I ask a dumb question or say something completely wrong! I was hoping to get a little advice before I start building something wrong! I am looking to power 4 5mm or 10mm blue LEDs, using a battery pack. Specs for LEDs: DC forward current: 30 mA Forward voltage: 2.7 V Again I have four LEDs, and want a battery pack that is not huge (please no C or D batteries). I am hoping for a few AA, A23, or 9V. I am having a hard time figuring out the following: 1. Which battery will last the longest with this setup? I am needing at least 5 hours of constant use. 2. Series or Parallel, and based on this how/where to add resistors? 3. Based on the above, what will be my resistor(s) of choice? 4. Based on the above, what will my battery life span be while fully lighting the LEDs?I have used the resistor calculators on several websites but they are lacking the information of mAh (specifically how long will my setup last on one battery pack), and/or how much of the battery am I wasting in my resistors. Thank you in advance for any help and advice!!