I want to power my Arduino Uno with four Nokia BL-5C 3.7V 1020 mAh Li-ion batteries. What would be best in terms of endurance: four batteries in series (with average voltage of 14.8V and 1020 mah), or 2x2 in parallel/series (with average voltage of 7.4V and 2040 mah). I guess what I'm basically trying to find out is whether there is a difference in efficiency in the Uno's step-down regulator, going from 14.8V down to 5V or from 7.4V to 5V. And perhaps there is a difference for the batteries discharging cycle. Any insights appreciated!