How about using 8.4V's headlights?
he will tell you that LED light headlamp can be as long as 3.7V, or more than 350 lumens are called light,
8.4V personal feeling is not the point, assuming inside the headlights installed lowering plate
there are several grades, the total capacity of the battery is recharged, the number is equipped with protection board and so on, these are key.
