On 2018-02-09 18:01, jbeattie wrote:
On Thursday, February 8, 2018 at 12:21:15 PM UTC-8, Joerg wrote:
On 2018-02-06 20:48, Jeff Liebermann wrote:

[...]


... Note that batteries are tested at a 0.2C discharge, which
yields larger numbers than the usual headlight discharge rate.
The Lezyne Deca 1500XXL claims 1500 lumens, which also seems a
bit high. Assuming 120 lumens/watt at a nominal 3.7V/battery,
that's: 1500 / 120 / 3.7 = 3.4A to run the headlight at full
brightness, or 1.7A per cell. Meanwhile, the cell capacity is
tested at: 0.2 * 2800 = 0.56A


Classic American answer: Then you need a bigger battery. On my road
bike I use eight 18650 cells, four in parallel and two of those
packs in series so the current on the cable to the front light
doesn't exceed 1A, at least not by much.

My MTB has to make do with four cells but except for short bursts
on city streets or fast county roads I drop that down from 8W to 3W
or sometimes even 1.5W in front.

I ride all roads in car traffic with lights, day and night, and
then usually at full bore. Bike paths sans DRL, singletrack with
just the front light lit so dirt bikers see me.

Get a low-watt blinker for daytime if you need a DRL. It's more
conspicuous than a fixed beam, depending on where you are riding. I
only use a DRL during morning hours, rainstorms or overcast
(sometimes). I use a little Nashbar flasher, which is pretty average
for riders around here.


My road bike front light has flash mode but when I tried it and walked
towards my bike it was annoying. Also, a bright constant light gives
more of an impression that some sort or motorcycle may be coming. So
people are more cautious than with "just a cyclist".


... My rain gear is high-viz, and I tend to avoid
all-black like some of my more fashionable cohorts. In daylight, I
see rider jerseys long before lights except under rare
circumstances.


It doesn't rain much out here. I prefer cotton and my wife does not like
high-viz T-shirts. They must be handwashed, else all other laundry in
that load appears with an orange or other tint.

I can't remember the last time I rode with rain gear. I just let myself
get wet or even soaked. When that starts to feel chilly I just step on
it until the water starts "steaming off".


I'm about to ride home, and if (after climbing out of the parking
garage) I decide to ride home on the frustrating cycle path, I will
encounter endless dopes with 1000 lumen lights pointed straight at
me. Oddly, because of the alignment of the cycletrack, I will not be
able to determine whether they are on-coming bicycles in the
side-by-side two-way bike lane or cars out on the road. The brighter
the light, the more it will look like a car -- and not a bike that
will pass me within five inches. One day, I will have a head-on if I
ride that path enough.


They probably don't have diffusor lenses, which they should. With those
installed my lights are roughly as bright as those of motorcycles.


A beam with cut-off and lower intensity would be much more noticeable
as a bike and would not blind me. A 1 watt flasher would make it
even more recognizable. One can justify a bright, less-shaped light
away from other riders, but blasting the retina burners around other
cyclists is unconscionable.


Everyone installing a high-powered LED light on a bicycle, front or
rear, should walk towards their lit bike during daylight and then again
at night. If the light is annoying, do something about it.

--
Regards, Joerg

http://www.analogconsultants.com/