Disclaimer: Forgive me if I phrase these questions poorly, I'm new to electronics. I am looking into a lighting system for my bicycle which would include something along the lines of a dual halogen bulb set-up powered by either a NiMh (14.4V 4000 mAh) or Li Ion (14.8V 4000 mAh) battery pack. Besides the weight issue, the Li ion is about half the weight, are there any other advantages (or disadvantages) to the Li ion pack? Also, I would like to include some LEDs on the bike as "running lights" to enable cars to see me better at night. The manufacturer of the Li ion battery states that other light systems should not be used with that particular set-up, but does nont make this claim for NiMh kits that they sell. I think Li ion batteries have a greater chance of explosion is used improperly, would this be a possibility if I powered maybe 8 LEDs along with the halogen bulbs? The LEDs are rated for use between 6 and 18 V and are pre-wired with resistors and 26g wire, so I think they should work. If they would indeed work, what would be the best way to hook them in with the existing lighting unit? If I haven't provided enough info, please let me know. Thanks.