If you run them in PARALLEL, that's the key, you can run 3-5 easily off 1 3volt battery. try and use a good coin battery like a 2032, that'll handle 10 LEDs easy.
Remember:
Series : basically "daisy chaining" the LEDs one after another. (+ from one to the - of the next, etc. In series, the voltage demand is
cumulative meaning if you ran 3 LEDs in series that draw 2.6 volts each you would need a battery pack that supplied at least 7.8 volts.
Parallel: Attaching the LEDs in such a way that
each LED's + and - touch the battery. In essence if we had the same rig in parallel, each LED would terminate at the battery, and the voltage demand would only be 2.6 volts, thus only one battery (3volt) would be needed. The amperage would be divided however, which may result in the LEDs not being as bright as their rated millicandella(brightness). This is usually not an issue and this is the preferred method for TF wire ups.
That's always tough. It's very hard to pre-build a harness without the figure in hand. You MUST take into account the twists and folds needed to TF from bot to alt mode. Your best bet is to PM him and send him the figure to wire up for you. I may be able to guide you but I owe out a bunch of work still, I'm so very far behind.
