Bodi wrote: (Oct06 on the subject of LEDs)The only bulbs that will make a difference are those that are on all the time - the headlight, tail light, and marker lights. Turn signals take a good shot of power, but are on so rarely that they won't affect charging.
Usually we want a brighter headlight so a lower power one is undesirable. LED headlights are coming but there aren't any yet.
Marker lights can just be disconnected, saving almost 15 Watts of power (0.6A each). If you really like the markers you should get LED conversions.
The tail/stop light uses another 1157 bulb, 7W on tail and 32W on stop. You can't eliminate the tail/stop lamp obviously. The stop light is only on occasionally but it's usually on when stopped and idling with the lowest alternator output. Reducing these loads will help maintain battery charge.
For the tail/stop lamp you need a really bright bulb; that's why the 1157 takes almost as much juice as the stock headlight low beam. You want the stop light to be very noticeable even in bright sun.
I have tried many LED lamp conversion clusters and found them to be dim, dim, dim, and dimmer - adequate at night but dangerously dim in sunlight. I have not tried the
www.customdynamics.com 38mm cluster claimed to be the brightest cluster made.
I am using the
www.superbrightleds.com Luxeon Star single LED 1157 replacement 1157-RLX3 in a standard Stanley large tail light unit. It is astoundingly bright, stunning at night and more than adequate in sunlight. Even with a single emitter there's enough light bounced around inside the reflector and lens to light up the license plate to an almost legal level (I think white light is required to be legal). It seems strange that one LED is brighter than an array or 30+ LEDS but it is. I'm certain this would beat the
www.customdynamics.com guarantee challenge.
The single LED is not applicable to the marker/turn signal units - you need a right angle LED unit. I have been unable to find a conversion 90 degree LED cluster with enough light to be useful so I just disconnect the markers and use the stock filament bulbs for turn signals. They take 50W or so when flashed ON but as mentioned that load is very infrequent. You can get complete LED marker/signal units and mount them somehow; making a complete assembly with adequate light is MUCH easier than making a conversion lamp to work with the stock lens and reflector.
Using LED turn signals will disable the stock flsher, it needs the higher load current from filament lamps. Adding "compensators" defeats the power saving of LED lamps - they are load resistors that draw the power a normal lamp would and just heat up. Just install a 3 wire electronic flasher and the LED signals will work with very little extra power draw. (The 3-wire flasher uses a bit of power to operate whereas the 2-terminal stock flasher uses the lamp power without any extra load)
More from Bodi (March 2008)The newer high efficiency LEDs make a lot of light from not much power. Using different materials and processes in the LED chip the light wavelength can be almost any visible colour, pretty far into the invisible IR end of the spectrum, and a bit past visible in the UV end. A LED chip will produce a very narrow colour spectrum - not quite a single wavelength but close enough to be equivalent visually.
White LEDs come in two types; multichip and phosphor. Multichip have 3 or 4 different colour LEDs in the same package, balanced to give a white looking light. Phosphor ones have a UV LED behind a phosphor blob that glows with a whitish light, actually a mix of phosphors with different colours that makes white much like the multichip version. The effect can be seen on a TV screen - close up you will see green, blue, and red spots but farther away these blend together to look like a single colour.
There are different approaches to either optimize "whiteness" - so colours look similar to how they would look in daylight, or to optimize luminous efficiency - the amount of light produced for the electrical power used.
The red tail-light lens blocks all wavelengths shorter than about 600nm (orangish red) - light from the bulb that's anywhere from oranger to blue is blocked and effectively wasted. A standard tail light bulb is a true "black body" radiator which radiates from long wavelength deep infrared all the way to a colour that is dependent on the filament temperature, with radiated power dropping off rapidly below that wavelength.
All filament bulbs - black body radiators - have plenty of light at wavelengths longer than their "colour temperature" rating, so a tail light will look plenty bright with any "white" filament bulb. There are exceptions where phosphor coatings and special gases in the bulb are used, but standard tail-light bulbs won't use these tricks.
Not true with a white LED. Mutichip types will be wasting the chips that aren't red. Phosphor ones will be wasting the non-reddish part of their spectrum. I'm trying to attach a spectrum for the Luxeon 3 white (phosphor) LED. You'll see (hopefully) that there's a fair bit of blue and a lot of yellow but a big drop from yellow-orange towards red.
So you will be pumping 3 watts of power into it and getting maybe 1/8 of the actual light from the LED seen as red through the tail-light lens.
If you use a luxeon 3 red (direct radiating) LED, all the light produced will be passed through the lens.
This is true for any white LED, it's a waste of power and a dimmer end result than using a red LED. Adding a white one pointed at the license plate will keep you "legal", but the actual tail/stop function should be red. Same for signals, amber LEDs will be brighter than the same power & efficiency white one.
I tried a lot of LED 1157 replacements and found them all woefully dim regardless of marketing hype, so I decided to make my own conversion.
I bought a bunch of red and white LEDs planning to make a multi-LED tail/stop light panel that will fit into a Stanley SOHC4 tail lamp with red for the tail/stop part - with side lighting too - and white license illumination. There are a few design decisions and the thing is NOT as simple to design as I had originally though, but hopefully I'll get it done. Unfortunately I found the Luxeon red single LED 3W 1157 replacemnt... it's definitely bright enough from straight back in daylight and more than sufficient at night from all angles with the stray light bouncing around inside the lens. The license is actually well lit, although an illegal red. I'm happy enough with this that I haven't done any serious work on the LED panel but I have been working on the electronics to drive the LEDs at full power over a decent voltage range and have the dim/bright ability for tail/stop use. I've hooked up a pulsed circuit recently that looks brighter than "full power" - you can overdrive a LED quite a lot in pulsed mode as long as the total power over time is below the rated maximum (like giving it 400% of maximum power for 25% of the duty cycle), and we apparently see the brighter pulses but don't notice the darkness between them. I noticed that many buses and trucks use pulsed LED tail lights - easy to see if you move your head around while looking at them as they leave a trail of dots rather than the line from an always-on one.
So I don't recommend white LEDs, is the basic message... got carried away with the ranting again.
