5 Watt LED lamps.

Marty Wallace said:

Has anyone tried out the 5 Watt LEDs?
I've just ordered one and I'm wondering how other people set theirs up. What
battery arrangement do you have and how long do they last? What lens angle
do you have, (if you use a lens?) Do you do road or MTB and is 5 Watts
enough for technical MTB? Is it handlebar or helmet mounted? Do you have a
multiple LED setup?

I had seriously considered LEDs as a replacement to halogens when I was last
replacing the lights on my bike.

After looking at the pros and cons, I opted to stay with halogens.

-As far as efficiency goes, the 5W luxeon leds are about as good as the best of
the halogens, if not better.

-The leds need heatsinking, halogens don't. (more space, possibly more weight).

-Halogens can be run directly off the battery (6 or 12v depending on the
bulbs), where the leds need a dedicated power supply. (extra cost).

-The white 5W luxeon leds have a quoted life of about 500 hours (to half
brightness if I recall correctly), your typical halogen is about 2000 hours
(till it burns out)

-Dollar for dollar, haloges are a LOT cheaper than the LEDs.

-If you're trying to extend life, LEDs are killed by heat, so the better
heatsinking you can apply to the led, the better. Halogens are killed by
overvoltage (even a bit), so the closer to the rated voltage you can supply
them, the better.

On an interesting but unrelated note, if you undervoltage halogens far
enough, their efficiency drops to something really shocking (forget about
battery power), and their life expectancy drops significantly too. (that's why
dimmers on home downlights is a stupid idea).

After all that, you can see why I stuck to halogens.

--
Linux Registered User # 302622 <http://counter.li.org>

Quoted message said:

On an interesting but unrelated note, if you undervoltage halogens far
enough, their efficiency drops to something really shocking (forget about
battery power), and their life expectancy drops significantly too. (that's

why

Quoted message said:

dimmers on home downlights is a stupid idea).

After all that, you can see why I stuck to halogens.

--
Linux Registered User # 302622

<http://counter.li.org>

I sort of suspected as much. I often wondered if there was much point to a
dimmer. A second lower wattage bulb would probably be more efficient.

Marty

Marty Wallace said:

I sort of suspected as much. I often wondered if there was much point to a
dimmer. A second lower wattage bulb would probably be more efficient.

And offer a whiter light.

--
Linux Registered User # 302622 <http://counter.li.org>

"John Tserkezis" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Marty Wallace said:

Halogens are killed by
overvoltage (even a bit), so the closer to the rated voltage you can

supply

Quoted message said:

them, the better.

Not entirely true.......you can overvolt halogens with out too many problems
as long as you have a circuit to provide a "soft startup" where you
gradually increase the voltage to the final voltage. This reduces the
stress to the globe caused by going from zero to full voltage in a single
step (ever notice how globes usually blow when you first turn them on?).

The advantage of overvolting halogens is that you get more light intensity
than the extra power you are pumping in (ie the halogens run more
efficiently). This is more bang for your buck as if your increase in
voltage results in a 10% increase in the power that the lamp is using, you
will get a corresponding increase of greater than 10% in the intensity of
the light.

I have run my 12V halogens using 11 NiMh cells (13.2V nominal) without any
problems thus far.....I am sure that I can remember reading a web site that
reckons that you can even add a 12th cell for 14.4V without too much drama.
You may reduce the total life of the globe from thousands of hours to
hundreds of hours but this is still a lot of night riding time.

Cheers,

Gags

Gags said:

Not entirely true.......you can overvolt halogens with out too many problems
as long as you have a circuit to provide a "soft startup" where you
gradually increase the voltage to the final voltage. This reduces the
stress to the globe caused by going from zero to full voltage in a single
step (ever notice how globes usually blow when you first turn them on?).

Bzzzt. Turn-on surge is more a problem with mains operated incadescent
bulbs, where the filament is quite thin and fragile. The turn-on surge,
something like 10 times normal operating current, shakes the filament to bits
if it's already weak.
Low voltage halogens have quite thick and rugged filaments, so don't suffer
from this problem.

And they DO have a shorter life when run above their rated voltage.

Quoted message said:

The advantage of overvolting halogens is that you get more light intensity
than the extra power you are pumping in (ie the halogens run more
efficiently). This is more bang for your buck as if your increase in
voltage results in a 10% increase in the power that the lamp is using, you
will get a corresponding increase of greater than 10% in the intensity of
the light.

It's a heck of a lot more than just "greater than 10%". With heck of a
reduction in operating life as well.

Quoted message said:

I have run my 12V halogens using 11 NiMh cells (13.2V nominal) without any
problems thus far.....I am sure that I can remember reading a web site that
reckons that you can even add a 12th cell for 14.4V without too much drama.
You may reduce the total life of the globe from thousands of hours to
hundreds of hours but this is still a lot of night riding time.

As long as you can acknowledge there is a significant reduction in life.
Operating life might not be an important issue to you, but we don't know that
everyone else might not care about life.

--
Linux Registered User # 302622 <http://counter.li.org>

John Tserkezis said:

Quoted message said:

The advantage of overvolting halogens is that you get more light intensity
than the extra power you are pumping in (ie the halogens run more
efficiently). This is more bang for your buck as if your increase in
voltage results in a 10% increase in the power that the lamp is using, you
will get a corresponding increase of greater than 10% in the intensity of
the light.

It's a heck of a lot more than just "greater than 10%". With heck of a
reduction in operating life as well.

Quoted message said:

I have run my 12V halogens using 11 NiMh cells (13.2V nominal) without any
problems thus far.....I am sure that I can remember reading a web site that
reckons that you can even add a 12th cell for 14.4V without too much drama.
You may reduce the total life of the globe from thousands of hours to
hundreds of hours but this is still a lot of night riding time.

As long as you can acknowledge there is a significant reduction in life.
Operating life might not be an important issue to you, but we don't know that
everyone else might not care about life.

Here's an example of a manufacturer that deliberately over-voltages.
They claim 38% greater light output with a 15% increase in power
consumption. Their bulbs should last around 1000 hours, instead of
"several thousand hours" if they weren't over-voltaged. Seemed like a
good equation to me. I can't comment on the actual lifespan yet,
since I've only had the light for a month or so...

Probably a good idea to use two lights instead of one, for when one
does die.

http://www.lumicycle.co.uk/over.html