Alan B wrote:The older LEDs have been about 70 lumens per watt, the newer ones are about 100 lumens per watt. Halogens are about 15 lumens per watt. Your choice.
That's not exactly true...
Halogen bulbs have a MIN of 35 lumens / watt..
NEWER - LEDs white.. Have never had more than 70 lumens / watt and those are EXPENSIVE ones... (the ones that put out the same as Xenon HiD (~110lm/watt) are REALLY expensive..)
Every single one of those normal costing LED flashlights say 900 Lumens and are $30...
My Halogen bulb is $18/pr or $9 each (actually replacement bulb is only $5) AND are double the lumens of those LED flashlights...
I have seen a $35 1200 lumen LED light, BUT it uses 12v - 2000mah.. So ok, my halogen uses 12v - 4000mah to produce 18-1900 lumens and that LED one will do 2400 lumens for the same power but it's 4 times the price and only gets 500 lumens more..
A xenon hid Kit with (electric) balasts are about $25 and give 3,200 lumen output!
Yes, of course, LEDs CAN last a LOT longer, but I've never had any luck with regular LEDs, either the control board or the actual LEDs burn out!
But like I said..
Halogen/Xenon for the price can't be beat..
UNLESS you can show me an LED Headlight/lamp for a bicycle (or a car) that puts out 1900 lumens, full spectrum White Light for less than $10 AND THEN I'LL BUY IT.
Your data may be out of date. Some of your numbers are beyond possible. 1900 lumens from 48 watts incandescent? That's 40 lumens per watt which is arc-lamp territory. Not likely, or not suitable for ebike use. You can push halogen bulbs to somewhat higher than usual efficiency by overvolting but at the first pothole they will fail. For vehicular use they must be operated at a lower temperature and efficiency for rugged service. Halogen bulbs are low cost, and the cycle replates tungsten onto the filament allowing the filament to have a longer life and be operated at a higher temperature than standard tungsten. But in the end it is still a tungsten bulb with only hot body efficiency.
A 12V 4A bulb is about 50 watts. At a generous 20 lumens per watt that is 1,000 lumens. That's bulb lumens, by the time you account for reflector loss and lens losses you get about 30-50% of that so maybe 500 lumens out the front. Hardly 1900 lumens, that's advertising smoke. A $30 "900 lumen LED" will also get about 500 lumens out the front. LEDs get about 70% out the front efficiency because much less of their light hits the reflector which is lossy. Filament bulbs radiate most of their energy into the reflector whereas LEDs concentrate it more out the front.
Why are you shouting?
By the way, it is not "12v 2000mah" - milliampere hours are incorrect units. Milliamps are the proper units for current. Time is not part of this.http://en.wikipedia.org/wiki/Luminous_efficacy
shows about 16-20 lumens per watt for halogen incandescents. Car headlights at 60 watts are rated at 1,000 lumens which is 16 lumens per watt. Some halogen lights are more efficient but the filaments are not designed for the high vibration environment of a vehicle, especially a bicycle. How long do your bulbs last? Are they designed for vehicle service? Bicycle service?? Bicycles are harder than motorcycles or cars on their lights due to the lack of suspension and vehicle mass.
From the same chart above you can see LEDs rated up to 150 watts per lumen (not including power supply). Not all power supplies are efficient, many flashlights are optimized for low cost rather than high efficiency. Good power supplies are 80-90% efficient. Adjusting for power supply efficiency makes only a small difference in overall efficiency.
The filament lights that show 35 watts per lumen are very short life bulbs such as photofloods or projector bulbs. They are operated at extreme temperatures to increase the efficiency, have short operating lives, cannot handle vibration and are unsuitable for bicycle use.
Bulb life and efficiency is a trade-off. High efficiency bulbs run at higher temperatures and the tungsten is closer to its melting point and more sensitive to vibration and physical damage. Tough filaments are longer lived, operate at lower temperatures and produce less light.
LEDs are rated for tens of thousands of hours of service, while filament bulbs have a wide range of ratings from a few tens of hours for bright photofloods on up. The longer the bulb life the lower the efficiency. The gasses used in the bulbs help the life in a complicated tradeoff. Bulb operating voltage changes the life and vibration sensitivity characteristics significantly as it affects filament temperature.
It seems odd to spend many hundreds to a few thousands of dollars on batteries, motors, brakes, tires, controllers and only $9 on the lights. I would rather have something small, rugged and efficient on my bike or ebike. One tank of gas in a vehicle costs more than a good LED headlight. To each his own.