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Old 03-22-08, 01:30 PM   #1
supton
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LED vs Halogen

Last summer I took a Home Depot 20W exterior spotlight and used it with a 7Ahr SLA. Good amount of light, even with a 20W halogen with no reflector on the bulb (the housing does have something of a reflector in it). My question is, would a couple of the newer LED lights, be it flashlight or similar, come close to the same light output? I have a hard time believing that something running on a couple of AA's, even if NiMH, is going to come close in light output.

I don't do much riding in the dark, but I'd like to have the option--but I'm loath to spend $$$ to do so. At the same time, I've got a new bike, and would have to figure out how to mount up this light. If I did, I'd be tempted to buy a cheapie LED light for the bracket, and run the battery in a handlebar bag; but OTOH I'm not sure I want that extra weight on the handlebar (it's a heavy battery).

If I could get some new LED lights that ran on rechargables (preferably AA, those will work in my camera too) and gave me an hour or so of run time for $50 or so, that'd be great. I also would prefer to use half-way decent mounts, as I would want the lights to be easy to remove for when I don't need them, or when I'm transporting the bike, etc. My night-time rides are quick 45minute or so rides for stress relief and excersise, not commuting, on lightly traveled and mostly-unlit roads.
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Old 03-22-08, 03:45 PM   #2
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Originally Posted by supton View Post
Last summer I took a Home Depot 20W exterior spotlight and used it with a 7Ahr SLA. Good amount of light, even with a 20W halogen with no reflector on the bulb (the housing does have something of a reflector in it). My question is, would a couple of the newer LED lights, be it flashlight or similar, come close to the same light output? I have a hard time believing that something running on a couple of AA's, even if NiMH, is going to come close in light output.

I don't do much riding in the dark, but I'd like to have the option--but I'm loath to spend $$$ to do so. At the same time, I've got a new bike, and would have to figure out how to mount up this light. If I did, I'd be tempted to buy a cheapie LED light for the bracket, and run the battery in a handlebar bag; but OTOH I'm not sure I want that extra weight on the handlebar (it's a heavy battery).

If I could get some new LED lights that ran on rechargables (preferably AA, those will work in my camera too) and gave me an hour or so of run time for $50 or so, that'd be great. I also would prefer to use half-way decent mounts, as I would want the lights to be easy to remove for when I don't need them, or when I'm transporting the bike, etc. My night-time rides are quick 45minute or so rides for stress relief and excersise, not commuting, on lightly traveled and mostly-unlit roads.
At the rated voltage of a halogen light, assuming an 20W MR16 bulb, the output is going greater than most LEDs. The halogen puts out 800 lumen while a commercial LED system like the MiNewt or TriNewt put out 190 lm and 450 lm, respectively. There might be better lamps out there now but those are typical. The TriNewt, as do many lamps, get the lumen count up by adding the output from several individual LEDs. While this is valid...the amount of light is the same...it's sneaky because the quality of the light isn't the same. Think of it as the difference between a search light and a equivalent number of car lights. A search light is going to penetrate further into the dark then the car lights will.

The real magic of halogen is the ability to sacrifice bulb life for light output. You can overdrive the halogen and boast the amount of light to incredible levels. Yes, the bulb lasts only 10% of a bulb run at nominal voltage. But for most halogens the life is going to be 5000 hrs at rated voltage and 500 hours at 20% overvolted. That still a long time. The bulb will eventually have to be replaced but the bulb is usually not the most costly part of a light system. For a the 20W bulb above, you can double the output for one more cell in your battery system. At 12V your system is pretty good in terms of light output and run time. Go to 14.4V and you'll be astounded.

LEDs do put out pretty good light for their weight. I just swapped over to my LEDs for the rest of the season (about 3 weeks for commuting) that I need lights. But, using the Fenix P1 for example, I'm not convinced that their light output is that good. The P1 puts out 180 lm for 1 hr. To get the same output as your light at 12V, you'd need 6 of them (they aren't that cheap). To get the light output at 14.4V, you'd need 9 of them (They really aren't that cheap!) I don't have that much bar space...even with a wide light bar I don't mind carrying batteries and would rather have the light output.
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Old 03-22-08, 04:20 PM   #3
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This should change fairly soon with the Seoul SSC P7 emitter, where brightness of 400+ lumens is being promised from 1 led.
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Old 03-22-08, 07:18 PM   #4
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Originally Posted by cyccommute View Post
At the rated voltage of a halogen light, assuming an 20W MR16 bulb, the output is going greater than most LEDs. The halogen puts out 800 lumen while a commercial LED system like the MiNewt or TriNewt put out 190 lm and 450 lm, respectively. There might be better lamps out there now but those are typical. The TriNewt, as do many lamps, get the lumen count up by adding the output from several individual LEDs. While this is valid...the amount of light is the same...it's sneaky because the quality of the light isn't the same. Think of it as the difference between a search light and a equivalent number of car lights. A search light is going to penetrate further into the dark then the car lights will.

The real magic of halogen is the ability to sacrifice bulb life for light output. You can overdrive the halogen and boast the amount of light to incredible levels. Yes, the bulb lasts only 10% of a bulb run at nominal voltage. But for most halogens the life is going to be 5000 hrs at rated voltage and 500 hours at 20% overvolted. That still a long time. The bulb will eventually have to be replaced but the bulb is usually not the most costly part of a light system. For a the 20W bulb above, you can double the output for one more cell in your battery system. At 12V your system is pretty good in terms of light output and run time. Go to 14.4V and you'll be astounded.

LEDs do put out pretty good light for their weight. I just swapped over to my LEDs for the rest of the season (about 3 weeks for commuting) that I need lights. But, using the Fenix P1 for example, I'm not convinced that their light output is that good. The P1 puts out 180 lm for 1 hr. To get the same output as your light at 12V, you'd need 6 of them (they aren't that cheap). To get the light output at 14.4V, you'd need 9 of them (They really aren't that cheap!) I don't have that much bar space...even with a wide light bar I don't mind carrying batteries and would rather have the light output.
Thanks; that's good info to know. I'll look into transfering my light and perhaps finding a different (lighter) battery.
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Old 03-22-08, 10:41 PM   #5
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Thanks; that's good info to know. I'll look into transfering my light and perhaps finding a different (lighter) battery.
A 4.5 Ahr NiMH battery will give you about 2 hours with a 20W bulb. Look at my post for how I do the batteries.
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Old 03-22-08, 10:48 PM   #6
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This should change fairly soon with the Seoul SSC P7 emitter, where brightness of 400+ lumens is being promised from 1 led.
The LEDs look promising but they still have a ways to go. A $3 20W 12 MR-16 puts out twice as much light. Juice it up and it'll put out nearly 4 times as much light. The LED may beat halogen in weight and run time but a halogen will out do just about anything else that is small enough to put on a bicycle
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Old 03-23-08, 06:58 AM   #7
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Dollars per lumen output, nothing beats an overvolted MR-16. Hands down.
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Old 03-23-08, 07:27 AM   #8
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Originally Posted by cyccommute View Post
The LEDs look promising but they still have a ways to go. A $3 20W 12 MR-16 puts out twice as much light. Juice it up and it'll put out nearly 4 times as much light. The LED may beat halogen in weight and run time but a halogen will out do just about anything else that is small enough to put on a bicycle
The other side of it though is that you never have to worry about an LED burning out. With the halogen (especially overvolted), it is only a matter of time.
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Old 03-23-08, 08:21 AM   #9
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Originally Posted by K6-III View Post
This should change fairly soon with the Seoul SSC P7 emitter, where brightness of 400+ lumens is being promised from 1 led.
They are already out:

http://www.dealextreme.com/details.dx/sku.11809

but from the picture you can see that they just have just made 4 emitters in one package. The beam pattern isn't going to be as good with this, in other words.

The lumens/watt ratings for these are ~ 80 which isn't bad, but it also isn't a real advance either. They are just packaging 4 of their older LEDs into one package to get the brightness up.

I think the point of this package is to go after the 60 and 100 watt light bulb market.

http://www.led-professional.com/content/view/930/29/
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Old 03-23-08, 09:01 AM   #10
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They are already out:

http://www.dealextreme.com/details.dx/sku.11809

but from the picture you can see that they just have just made 4 emitters in one package. The beam pattern isn't going to be as good with this, in other words.

The lumens/watt ratings for these are ~ 80 which isn't bad, but it also isn't a real advance either. They are just packaging 4 of their older LEDs into one package to get the brightness up.

I think the point of this package is to go after the 60 and 100 watt light bulb market.

http://www.led-professional.com/content/view/930/29/
Efficient optics is much more important than raw lumen numbers. I just finished my new dynamo powered light using 2 SSC P4 emitters from DX, Fraen 15X30 and 10 degree lens with holders, and installed them in a standard wet location aluminum electrical outlet box. This provides an armored, waterproof, off the shelf housing for just a few dollars.



In this photo you can see the how different the lenses are.



I've built and ran an MR-16 20 watt light with a 12 volt-7 amp hour jell cell battery and the above light provides more usable light powered with a bottle type dynamo for unlimited runtime, which is perfect for my touring bike. Here is the link where you can find many circuits for powering high power LED's from a dynamo.

http://www.pilom.com/BicycleElectron...moCircuits.htm

After building this light I'll never go back to batteries!
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Old 03-23-08, 10:04 AM   #11
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The other side of it though is that you never have to worry about an LED burning out. With the halogen (especially overvolted), it is only a matter of time.
That's why I always carry multiple lights. Even if I use LED I have more then one. However, with the halogens I've used for the past 15 years, I've only ever blown out one lamp. I know it can happen at any point but, for me at least, it's a very rare event
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Old 03-23-08, 06:51 PM   #12
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Originally Posted by supton View Post
Last summer I took a Home Depot 20W exterior spotlight and used it with a 7Ahr SLA. Good amount of light, even with a 20W halogen with no reflector on the bulb (the housing does have something of a reflector in it). My question is, would a couple of the newer LED lights, be it flashlight or similar, come close to the same light output? I have a hard time believing that something running on a couple of AA's, even if NiMH, is going to come close in light output.
...
My night-time rides are quick 45minute or so rides for stress relief and excersise, not commuting, on lightly traveled and mostly-unlit roads.
20w halogens put out a decent amount of light. You will need 2-3 led "flashlights" to match this. Two would be a good compromise. A 7Ahr battery is a big thing to lug around so you might find the reduced output ok given the increased convenience. I could never find a good way to carry a SLA, but a half a dozen AAs is easy to strap to the frame. You are probably looking at 500lm from the light you have. My last three LED light have been around this and its plenty.

Overvolted halogens are great on paper, In practice as your battery discharges it doesn't maintain the voltage needed to produce the equivalent LED efficiency and those big lumen numbers.
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Old 03-23-08, 09:01 PM   #13
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20w halogens put out a decent amount of light. You will need 2-3 led "flashlights" to match this. Two would be a good compromise. A 7Ahr battery is a big thing to lug around so you might find the reduced output ok given the increased convenience. I could never find a good way to carry a SLA, but a half a dozen AAs is easy to strap to the frame. You are probably looking at 500lm from the light you have. My last three LED light have been around this and its plenty.

Overvolted halogens are great on paper, In practice as your battery discharges it doesn't maintain the voltage needed to produce the equivalent LED efficiency and those big lumen numbers.
That's not been my experience. The lamps I have put out the same quality and quantity of light for the 1.5 to 2 hours I use them. That's using NiMH batteries which have a flatter discharge curve than SLA. And 4.5 Ahr batteries will last about 2.5 hours.
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Old 03-24-08, 09:36 AM   #14
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That's not been my experience. The lamps I have put out the same quality and quantity of light for the 1.5 to 2 hours I use them. That's using NiMH batteries which have a flatter discharge curve than SLA. And 4.5 Ahr batteries will last about 2.5 hours.
+1

I'm running twin 20W halogens @ 14.4V and I've never had my lights go noticeably dim on me until they are just about ready to discharge fully. They may be getting dimmer as I ride, but I can't see the difference... so I don't care. I'm using a 5Ah NiMH battery, and I get about 1.5 hours of runtime when I'm at full flamethrower mode.

The one thing that I did for my lighting system is installed a Lightbrain controller. It has more slick and useful features than you can shake a stick at... the best $38 I've spent in a long time.
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Old 03-24-08, 11:27 AM   #15
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I did the overvolted halogen thing for a couple years and finally gave up in disgust and am currently running 2 Fenix lights.

Here's the plus & minus of each in my book:

Halogen:
+ can be cheap, bright, efficient, color temperature (i like the halogen yellow-white light)
- expensive if made reasonably light (li-ion batteries are $$$), multiple connectors = many failure points, never entirely waterproof, poor experience with overvolting (blew bulbs at least every 100hrs at 20% overvolted). Off the shelf solutions are pricey.
Summary: cheap, bright, lightweight: choose 2. And you still won't have 100% reliability.

LED:
+ lightweight, reliable, can take standard AA or cr123a batteries. More lumens/$$ than commercial halogen systems.
- less lumens/$$ verses homebrew halogen, LED color temp (more blue than I'd prefer, washes out some detail).

Summary: after using both, I'm sticking with my dual Fenix flashlight setup. just over $100, over 400 lumens on hi (p3d's rule!), super flexible, use & abuse the heII out of em and they just don't care. No mainteance, set & forget the lights, just charge the batteries. oh yeah, and they make awesome flashlights

fwiw.... I've converted a few users to Fenix as well. One dude was using HID, took a tumble and blew the bulb. Got 2 Fenix and has never been happier.

Cheers
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Old 03-26-08, 07:23 PM   #16
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A few years ago when I did the calculations the break-even point between LED and halogen was about 8 Watts. That is, you got more light from LEDs under 8 Watts, and more light from Halogen over 8 Watts. So you have to choose how long you want your batteries to last (Watts vs time), and how much light you need, and pick which side of that fence you fall on. For instance my tail light is a 1 Watt luxeon, and runs on a pair of AA NIMH batteries for about 3-5 weeks between charges. The headlight I was building had 4 1 Watt luxeons, and would have used something like a 6 or 8 AA NIMH pack. However, my 1 Watt cateye luxeon headlight was fine for my needs so I never finished the homebrew headlight yet.
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