The last headlight you will ever need

On Tue, 25 Mar 2014 08:50:01 -0700, sms
wrote:

On 3/25/2014 2:40 AM, somebody wrote:
Now I have seen everything:

http://www.fasttech.com/products/1/1...-3-mode-3200lm

3200 lumens is pretty lame. See
http://www.aliexpress.com/item/free-shipping-5000-Lumen-2x-CREE-XM-L-T6-LED-Bike-Bicycle-Light-Headlamp-Flashlight/1492257169.html

Yes, that beats it but does not have the 'wow' factor...


Jeff the Cyclist would pick the 7-light version. Obligatory links for
those unfamiliar...

http://www.gocomics.com/pearlsbeforeswine/2013/01/13

http://www.gocomics.com/pearlsbeforeswine/2014/02/27

On Tue, 25 Mar 2014 08:53:15 -0700, Jeff Liebermann
wrote:

On Tue, 25 Mar 2014 05:40:39 -0400, somebody
wrote:

Now I have seen everything:
http://www.fasttech.com/products/1/1...-3-mode-3200lm

Seven Cree T6 lights (10 watts or 3v @ 3A max).
http://www.cree.com/~/media/files/cree/led%20components%20and%20modules/xlamp/data%20and%20binning/xlampxml.pdf
I'll assume that they run it at 1A to keep the heat down.

The battery pack is too small and is not going to work. The lamp data
sheet shows that the 8.4v battery pack is six 18650 cells, which are
running at 1A output. So, how is this thing suppose to light up LED's
that can use up to 3A with only 1 watt max? I don't see an LED
driver/inverter anywhere. An 8.4v @1A battery pack will deliver 8.4
watts. Yet, the lights can conceivably use 6-10 watts *EACH* or more
conservatively, about 3 watts *EACH* if running at 1A. Assuming 3
watts per lamp for a total of 21 watts, an 8.4 watt battery pack can
run the lights to about 25% battery capacity remaining in 18 minutes.
Sounds great for very short rides.

I gotta get back to work, but this was too good to ignore. Thanks.

Magic. If you buy the light you receive, after the check clears, a
special incarnation that causes the lights to use only a fraction of
the wattage that they normally would use.
--
Cheers,

John B.

On Tue, 25 Mar 2014 11:04:34 -0700, sms
wrote:

The actual manufacturer information doesn't claim any of that stuff
http://www.trustfire.net.cn/product/1723645844-219463416/2014_newest_TrustFire_factory_D013_high_power_led_ bike_light_3200Lm_7_CREE_XM_L_2_waterproof_led_bik e_light.html

Yep. He leaves out the only number of importance, the actually
current drain at the various power levels. Also, I'm wondering how he
converts the 8.4V to the 3.0V necessary to power the lights.

Those batteries are certainly able to deliver 4A.

Ok, let's do the math. (Note: I had 2 hrs sleep last night and will
surely make at least one major math screwup here).

The 8.4 battery pack has 6ea 18650 cells. Each cell is rated at 3.7V
and optimistically 3A-hr drain. My limited imagination can't seem to
conjure how to wire 6ea 3.7V batteries into something that produces
8.4 volts. My best guess is that the author of the data sheet can't
add and that the voltage should really 7.4V, which is 2 cells in
series, and 3 strings in parallel. Yeah, that makes more sense. That
produces a 7.4V at 9A-hr battery pack. One can drain such a battery
pack to about 25% of rated capacity without killing the battery, so
that produces a:
7.4V * 9A-hr * 0.75 = 50 watt-hr
capacity battery pack.

Next, the current drain of the lights. The title says 3200 lumens,
but the table in the data sheet says 2100 lumens in "hi" mode. I'll
take the lower number as closer to reality. With 7 lights, that's 300
lumens per light. Diving into the Cree data sheet at:
http://www.cree.com/~/media/files/cree/led%20components%20and%20modules/xlamp/data%20and%20binning/xlampxml.pdf
the T6 lamp delivers a rated 280 lumens. 300 lumens would be 110% of
rated power. Looking at Relative Flux vs Current graph, 110% requires
800ma current. Seven of those lights would be 5.6 Amps in high power.
The power drain would be:
3.0V * 5.6A = 16.8 watts
A 50 watt-hr battery capacity with a 16.8 watt load will produce:
50 / 16.8 = 3 hrs
operating time. However, that assumes 100% efficiency in converting
the 8.4V to 3.0V to run the lights. I don't see any evidence of a
switcher, but there might be one buried inside the aluminum heat sink
or battery pack. I'll give it 80% efficiency, which yields:
3 hrs * 0.80 = 2.4 hrs
That's not as bad as I initially thought.

The big question is whether you can power them from a hub dynamo!

I can't, but maybe someone with tree trunk legs can do better.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 26/03/14 13:22, Jeff Liebermann wrote:
On Tue, 25 Mar 2014 11:04:34 -0700, sms
wrote:

The actual manufacturer information doesn't claim any of that stuff
http://www.trustfire.net.cn/product/1723645844-219463416/2014_newest_TrustFire_factory_D013_high_power_led_ bike_light_3200Lm_7_CREE_XM_L_2_waterproof_led_bik e_light.html

Yep. He leaves out the only number of importance, the actually
current drain at the various power levels. Also, I'm wondering how he
converts the 8.4V to the 3.0V necessary to power the lights.

Those batteries are certainly able to deliver 4A.

Ok, let's do the math. (Note: I had 2 hrs sleep last night and will
surely make at least one major math screwup here).

The 8.4 battery pack has 6ea 18650 cells. Each cell is rated at 3.7V
and optimistically 3A-hr drain. My limited imagination can't seem to
conjure how to wire 6ea 3.7V batteries into something that produces
8.4 volts. My best guess is that the author of the data sheet can't
add and that the voltage should really 7.4V, which is 2 cells in
series, and 3 strings in parallel. Yeah, that makes more sense. That
produces a 7.4V at 9A-hr battery pack. One can drain such a battery
pack to about 25% of rated capacity without killing the battery, so
that produces a:
7.4V * 9A-hr * 0.75 = 50 watt-hr
capacity battery pack.

Next, the current drain of the lights. The title says 3200 lumens,
but the table in the data sheet says 2100 lumens in "hi" mode. I'll
take the lower number as closer to reality. With 7 lights, that's 300
lumens per light. Diving into the Cree data sheet at:
http://www.cree.com/~/media/files/cree/led%20components%20and%20modules/xlamp/data%20and%20binning/xlampxml.pdf
the T6 lamp delivers a rated 280 lumens. 300 lumens would be 110% of
rated power. Looking at Relative Flux vs Current graph, 110% requires
800ma current. Seven of those lights would be 5.6 Amps in high power.
The power drain would be:
3.0V * 5.6A = 16.8 watts
A 50 watt-hr battery capacity with a 16.8 watt load will produce:
50 / 16.8 = 3 hrs
operating time. However, that assumes 100% efficiency in converting
the 8.4V to 3.0V to run the lights. I don't see any evidence of a
switcher, but there might be one buried inside the aluminum heat sink
or battery pack. I'll give it 80% efficiency, which yields:
3 hrs * 0.80 = 2.4 hrs
That's not as bad as I initially thought.

The big question is whether you can power them from a hub dynamo!

I can't, but maybe someone with tree trunk legs can do better.


I'm not even going to check your math and assumptions, because the
thought of such a light is stupid to begin with. I saw 3200lm and
thought "********".

That said, assuming some reasonable level of dynamo efficiency, you'd
need to produce something in the region of 20W mechanical to get 16.8W
electrical.

Considering my average power output estimate for last nights ride was a
conservative 213W (conservative because with 2 water bottles and other
stuff I'm a bit heavier than I told Strava), that's about 10% of my
total average output.

I reckon I could do it - but my 80lux IQ-TEC Premium was fine, even on
the busy 80km/h arterial roads I was riding on in the darkness.

--
JS

On Wed, 26 Mar 2014 14:52:26 +1100, James
wrote:

That said, assuming some reasonable level of dynamo efficiency, you'd
need to produce something in the region of 20W mechanical to get 16.8W
electrical.

That's an efficiency of 84%, which methinks is rather optimistic. Some
dynamo testing he
http://www.myra-simon.com/bike/dynotest.html
While one went as high as 60% efficiency, most of the commodity
dynamos ran about 30%. That would be 56 watts of person power needed
to deliver the necessary 16.8 watts electricity to power the light.

Also, I blundered into this article on using a bicycle to generate
electricity. I haven't read it in detail, but basically the author
suggests it's a lousy idea.
http://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html

Considering my average power output estimate for last nights ride was a
conservative 213W (conservative because with 2 water bottles and other
stuff I'm a bit heavier than I told Strava), that's about 10% of my
total average output.

With a 30% efficient dyanamo, change that to about 26% of your total
average output.

I reckon I could do it - but my 80lux IQ-TEC Premium was fine, even on
the busy 80km/h arterial roads I was riding on in the darkness.

What? You don't want 3200 lumens to scorch the paint on the cars
ahead of you? Fire Phaser one, six more to go.

Hmmm... I think I need to get some sleep.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 26/03/14 16:02, Jeff Liebermann wrote:
On Wed, 26 Mar 2014 14:52:26 +1100, James
wrote:

That said, assuming some reasonable level of dynamo efficiency, you'd
need to produce something in the region of 20W mechanical to get 16.8W
electrical.

That's an efficiency of 84%, which methinks is rather optimistic. Some
dynamo testing he
http://www.myra-simon.com/bike/dynotest.html
While one went as high as 60% efficiency, most of the commodity
dynamos ran about 30%. That would be 56 watts of person power needed
to deliver the necessary 16.8 watts electricity to power the light.

SP claims 72% for theirs.

This claims 67% for a SON.
http://www.ctc.org.uk/file/public/fe...ub-dynamos.pdf


Also, I blundered into this article on using a bicycle to generate
electricity. I haven't read it in detail, but basically the author
suggests it's a lousy idea.
http://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html

Considering my average power output estimate for last nights ride was a
conservative 213W (conservative because with 2 water bottles and other
stuff I'm a bit heavier than I told Strava), that's about 10% of my
total average output.

With a 30% efficient dyanamo, change that to about 26% of your total
average output.

I reckon I could do it - but my 80lux IQ-TEC Premium was fine, even on
the busy 80km/h arterial roads I was riding on in the darkness.

What? You don't want 3200 lumens to scorch the paint on the cars
ahead of you? Fire Phaser one, six more to go.

Hmmm... I think I need to get some sleep.


Yep, you do.

--
JS

On Tue, 25 Mar 2014 19:22:12 -0700, Jeff Liebermann
wrote:

On Tue, 25 Mar 2014 11:04:34 -0700, sms
wrote:

The actual manufacturer information doesn't claim any of that stuff
http://www.trustfire.net.cn/product/1723645844-219463416/2014_newest_TrustFire_factory_D013_high_power_led_ bike_light_3200Lm_7_CREE_XM_L_2_waterproof_led_bik e_light.html

Yep. He leaves out the only number of importance, the actually
current drain at the various power levels. Also, I'm wondering how he
converts the 8.4V to the 3.0V necessary to power the lights.

Those batteries are certainly able to deliver 4A.

Ok, let's do the math. (Note: I had 2 hrs sleep last night and will
surely make at least one major math screwup here).

The 8.4 battery pack has 6ea 18650 cells. Each cell is rated at 3.7V
and optimistically 3A-hr drain. My limited imagination can't seem to
conjure how to wire 6ea 3.7V batteries into something that produces
8.4 volts. My best guess is that the author of the data sheet can't
add and that the voltage should really 7.4V, which is 2 cells in
series, and 3 strings in parallel. Yeah, that makes more sense. That
produces a 7.4V at 9A-hr battery pack. One can drain such a battery
pack to about 25% of rated capacity without killing the battery, so
that produces a:
7.4V * 9A-hr * 0.75 = 50 watt-hr
capacity battery pack.

Next, the current drain of the lights. The title says 3200 lumens,
but the table in the data sheet says 2100 lumens in "hi" mode. I'll
take the lower number as closer to reality. With 7 lights, that's 300
lumens per light. Diving into the Cree data sheet at:
http://www.cree.com/~/media/files/cree/led%20components%20and%20modules/xlamp/data%20and%20binning/xlampxml.pdf
the T6 lamp delivers a rated 280 lumens. 300 lumens would be 110% of
rated power. Looking at Relative Flux vs Current graph, 110% requires
800ma current. Seven of those lights would be 5.6 Amps in high power.
The power drain would be:
3.0V * 5.6A = 16.8 watts
A 50 watt-hr battery capacity with a 16.8 watt load will produce:
50 / 16.8 = 3 hrs
operating time. However, that assumes 100% efficiency in converting
the 8.4V to 3.0V to run the lights. I don't see any evidence of a
switcher, but there might be one buried inside the aluminum heat sink
or battery pack. I'll give it 80% efficiency, which yields:
3 hrs * 0.80 = 2.4 hrs
That's not as bad as I initially thought.

The big question is whether you can power them from a hub dynamo!

I can't, but maybe someone with tree trunk legs can do better.

I suspect that their target market doesn't do either math or
electronics :-)
--
Cheers,

John B.

On 3/25/2014 4:57 PM, somebody wrote:
On Tue, 25 Mar 2014 09:18:57 -0400, Duane
wrote:

On 3/25/2014 9:02 AM, Sir Ridesalot wrote:
On Tuesday, March 25, 2014 5:40:39 AM UTC-4, somebody wrote:
Now I have seen everything:



http://www.fasttech.com/products/1/1...-3-mode-3200lm
Notice how close the light is to the beam shown? Notice the nice hot spot on that beam? Over 6.75 inches wide (172mm) and it goes on your handlebars?

Sounds and looks like a bunch of flashlights mounted together but not giving a very useful beam pattern to see the road surface with.

In strobe mode that light will be most annoying to anyone approaching it from in front.

I'd pass on it too.

Cheers

I wouldn't have to turn it on to reject it. I can't imagine mounting a
piece of junk like that on my bars.

But I think the OP's point was to be sarcastic, no?
Yes, I forgot the sarcasm header...

But is there one floating out there with even more LEDs?

Maybe with a bat signal?

On 3/26/2014 1:02 AM, Jeff Liebermann wrote:


Also, I blundered into this article on using a bicycle to generate
electricity. I haven't read it in detail, but basically the author
suggests it's a lousy idea.
http://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html

It's certainly a lousy idea if the intent is to use electricity to drive
devices that can reasonably be driven mechanically. Consider what it
would take to generate and store electricity to run an electric can
opener, vs. just cranking a manual can opener for 15 seconds.

Many years ago, we were asked to donate appliances, etc. to an
impoverished immigrant family that had moved to our area. Among our
donations was a manual can opener. The woman accepting donations was
astonished - "Do those things still work?" etc. She'd used only an
electric one for years. But earlier still, when we were given an
electric one as a gift, we returned it to the store.

Bicycling for transportation does have very high efficiency, but that's
the result of a different factor. When a person rides a bike, they're
not hauling around 3000 pounds of metal, plastic, rubber and glass. The
moving mass is almost all payload.

Related: http://www.bicyclinglife.com/Effecti...cacy/bacon.htm

--
- Frank Krygowski

On Wednesday, March 26, 2014 11:28:00 AM UTC-4, Frank Krygowski wrote:
On 3/26/2014 1:02 AM, Jeff Liebermann wrote:





Also, I blundered into this article on using a bicycle to generate

electricity. I haven't read it in detail, but basically the author

suggests it's a lousy idea.

http://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html



It's certainly a lousy idea if the intent is to use electricity to drive

devices that can reasonably be driven mechanically. Consider what it

would take to generate and store electricity to run an electric can

opener, vs. just cranking a manual can opener for 15 seconds.



Many years ago, we were asked to donate appliances, etc. to an

impoverished immigrant family that had moved to our area. Among our

donations was a manual can opener. The woman accepting donations was

astonished - "Do those things still work?" etc. She'd used only an

electric one for years. But earlier still, when we were given an

electric one as a gift, we returned it to the store.



Bicycling for transportation does have very high efficiency, but that's

the result of a different factor. When a person rides a bike, they're

not hauling around 3000 pounds of metal, plastic, rubber and glass. The

moving mass is almost all payload.



Related: http://www.bicyclinglife.com/Effecti...cacy/bacon.htm



--

- Frank Krygowski

In the rticle from the first link they talk about dead zones in the pedal cycle when using a bicycle to power a generator on a bicycle type trainer. I wonder if BioPace or other oval chainrings would help there?

Cheers

Cheers