Cuda2K, I use a 50 watt very narrow spot at 12 degrees and enough unreflected light goes out the front of the bulb to light up a two lane road and the shoulders as well. A 24 degrees 'flood' would seem to waste light in the trees and fields along side the road and not put light on and further down the road. As MR16 bulbs are inexpensive please try the narrowest spot you can find at least once. The only bulb I have ever had too tight a beam was a PAR36 shielded filament spotlight. As far as the batteries go, I vote for the 13.2 V battery. Wiring losses and connection resistances will drop the voltage at the bulb to 12 V or a harmless bit of overvoltage. Go with a 12 v battery and it might be underpowered. Given adequate money I would like a 18 to 24 V battery and a variable voltage regulator.