Bill Wright wrote:
John Williamson wrote:

The efficiency savings for mobile use aren't worth bothering about
except for applications like battery powered cycle lights or torches,
as the power used by the lighting on a car is a small percentage of
the total power used to move it. At 30mph on a flat road, the absolute
maximum total lighting load on most cars, including headlamps and
foglamps, is less than 400 watts, as against ten kilowatts or more
being used to overcome rolling and air resistance.

If that 400W could be reduced to 100W there would be worthwhile fuel
savings.

Less than 3% at constant speed in town, less at higher speeds or when
accelerating. Stopping at one red traffic light in a five mile journey
would make more difference. Correcting the tyre pressures every time the
load changes can make more difference. Removing the toolbox or shopping
from the boot makes almost as much difference. The absolute maximum on
my car is 210W, and that's using high beam headights and rear fog lights
while I'm signalling a turn.

To get the maximum lighting load down to 100W, you'd need to replace the
headlights with ultra efficient lights, which at the moment isn't
practical. In town, using dipped beams, the load is more like 150W,
anyway. You'll only use 400W in a situation where you are driving in
foggy conditions or using four high power halogen main beam lights.

--
Tciao for Now!

John.