This is really great news. For one thing, I don’t need an energy-wasting, heat-generating voltage regulator at all. And for another, I can stack all four batteries in parallel. This has the advantage that if I have a battery failure in the field, I just have less juice – I don’t have to take two batteries offline because of a single failure (as I would in a series-parallel setup).
I have one 1300mAh LiPoly battery, and I just ordered another one. I will put those two in series and run the Arduino Mega off that, and use the four big 2700mAh batteries in parallel to run the LED buss. This weekend I’ll do a test to see how long those four batteries can run the LEDs at full brightness before the voltage drops below 3.8V — that’s where the LEDs will start acting wonky.
Here’s the current-versus-brightness-value graph for the parallel setup.