If you're going to stick with the 5500, I wouldn't worry about running the LEDs off of it. The difference i flight time isn't likely to be noticeable. If you do want to go with a dedicated battery for lighting, I'd recommend going 5v, so you can run off a 2s pack and save weight. I only use a 1000mah 2s for my FPV stuff, it doesn't weigh a lot and I'm pretty sure you wouldn't even need one that big.