Originally Posted by
cyccommute
So what LED is the Cateye using that allows it to put out 800 lumens for 2 hours on a 3.2Ahr battery? I really am asking out of curiosity.
However, looking at the
We Test Lights website, it looks to me like they kind of fudge the light output. The Chinese Cree you linked to gives has a consistent light (if too low) light output over the 4 h run time while the Cateye has a spike of 800 lumens that only lasts a few minutes and then seems to dim with time over the 2 hours of run time to a very dim 92 lumens. It's not fair to say that the light has an output of 800 lumens if that output is only a spike at the beginning.
And, from the standpoint of a commuter, this is kind of a dangerous trend. I tell people that want to ride at night that it is a little known fact that it gets dark when the sun goes down. It's a bit facetious but my point is that on the ride home, it gets darker. With these smaller units, the constant dimming of the light means that you are going to get
less light just as you need
more light. On the morning part of the commute, it doesn't really matter because it's getting lighter all the time but at night, you simply don't want your lights to fail.
Looking around at similar lights, this seems to be how these lights work. They are bright initially but quickly fade.
I do want to thank you for the link to the website. Although I think the test on the Bright Eyes is wrong, it is still a useful site.
Yes. You are correct. My error.
A CREE T6 will produce 800 lumens given enough power (at 3A and 3.35V, a T6 will do about 1,000 lumens but that's 10W of heat to dissipate!), which the Volt800 can do and like you said, because of how Lithium battery works, it can't give 2 straight hours at 800 lumens out of that battery. Voltage will drop as soon as the light draining power and at full brightness, that's a lot of power being drained from that single 3.6V battery Lithium battery. On the Chinese light I had, it had four 18650 battery (two in parallel/series combo). CREE LED nominal voltage is 3.2 volt so the battery pack has to regulate voltage from 7.2V to 3.2V. Dropping 4V and sinking 2A from that regulator (8W), would create lots of heat (more than the LED itself!), hence why I guess they can't produce the rated lumens, their circuitry can't handle it.
Like I mention elsewhere, I hardly ride in full brightness, but it's there when I need it. I'm mostly in HyperConstant mode and will switch (by a quick double press of the button) to high mode when conditions requires it (like when a car coming toward me with his hi-beam or riding fast in a completely unlit path) so even after my 1 hour ride, light output is still strong and constant. If however this would become a issue, I could swap the battery with a fresh one. This, in my opinion, is more practical than carry 3 cheap Chinese lights on my (already crowded) handlebar with their corresponding battery pack hooked on my top tube, but that's just me, each his own.